diff --git a/.overcommit.yml b/.overcommit.yml
new file mode 100644
index 0000000..2e2bd2c
--- /dev/null
+++ b/.overcommit.yml
@@ -0,0 +1,36 @@
+# Use this file to configure the Overcommit hooks you wish to use. This will
+# extend the default configuration defined in:
+# https://github.com/brigade/overcommit/blob/master/config/default.yml
+#
+# At the topmost level of this YAML file is a key representing type of hook
+# being run (e.g. pre-commit, commit-msg, etc.). Within each type you can
+# customize each hook, such as whether to only run it on certain files (via
+# `include`), whether to only display output if it fails (via `quiet`), etc.
+#
+# For a complete list of hooks, see:
+# https://github.com/brigade/overcommit/tree/master/lib/overcommit/hook
+#
+# For a complete list of options that you can use to customize hooks, see:
+# https://github.com/brigade/overcommit#configuration
+#
+# Uncomment the following lines to make the configuration take effect.
+
+PreCommit:
+  RuboCop:
+    enabled: true
+    #command: ['bundle', 'exec', 'rubocop'] 
+    on_warn: fail # Treat all warnings as failures
+#
+#  TrailingWhitespace:
+#    exclude:
+#      - '**/db/structure.sql' # Ignore trailing whitespace in generated files
+#
+#PostCheckout:
+#  ALL: # Special hook name that customizes all hooks of this type
+#   quiet: true # Change all post-checkout hooks to only display output on failure
+#
+#  IndexTags:
+#    enabled: true # Generate a tags file with `ctags` each time HEAD changes
+CommitMsg:
+  CapitalizedSubject:
+      enabled: false
diff --git a/Gemfile b/Gemfile
index 81abda6..380384e 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,9 +1,9 @@
 source "https://rubygems.org"
 
-gem "rake"
+gem "rake", ">=10.4.2"
 
-gem "github_api"
-gem "colorize"
+gem "github_api", ">=0.12.3"
+gem "colorize", ">=0.7.7"
 
 group :test do
   gem "rspec"
diff --git a/Gemfile.lock b/Gemfile.lock
index 1287b76..ed27b31 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,24 +1,24 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    addressable (2.3.7)
+    addressable (2.3.8)
     ast (2.0.0)
     astrolabe (1.3.0)
       parser (>= 2.2.0.pre.3, < 3.0)
     codeclimate-test-reporter (0.4.7)
       simplecov (>= 0.7.1, < 1.0.0)
-    colorize (0.7.5)
-    coveralls (0.7.12)
-      multi_json (~> 1.10)
+    colorize (0.7.7)
+    coveralls (0.8.1)
+      json (~> 1.8)
       rest-client (>= 1.6.8, < 2)
-      simplecov (~> 0.9.1)
+      simplecov (~> 0.10.0)
       term-ansicolor (~> 1.3)
       thor (~> 0.19.1)
     descendants_tracker (0.0.4)
       thread_safe (~> 0.3, >= 0.3.1)
     diff-lcs (1.2.5)
     docile (1.1.5)
-    domain_name (0.5.23)
+    domain_name (0.5.24)
       unf (>= 0.0.5, < 1.0.0)
     faraday (0.9.1)
       multipart-post (>= 1.2, < 3)
@@ -30,11 +30,12 @@ GEM
       multi_json (>= 1.7.5, < 2.0)
       nokogiri (~> 1.6.3)
       oauth2
-    hashie (3.4.0)
+    hashie (3.4.1)
     http-cookie (1.0.2)
       domain_name (~> 0.5)
-    jwt (1.4.1)
-    mime-types (2.4.3)
+    json (1.8.2)
+    jwt (1.5.0)
+    mime-types (2.5)
     mini_portile (0.6.2)
     multi_json (1.11.0)
     multi_xml (0.5.5)
@@ -48,10 +49,10 @@ GEM
       multi_json (~> 1.3)
       multi_xml (~> 0.5)
       rack (~> 1.2)
-    parser (2.2.0.3)
+    parser (2.2.2.2)
       ast (>= 1.1, < 3.0)
-    powerpack (0.1.0)
-    rack (1.6.0)
+    powerpack (0.1.1)
+    rack (1.6.1)
     rainbow (2.0.0)
     rake (10.4.2)
     rest-client (1.8.0)
@@ -62,45 +63,45 @@ GEM
       rspec-core (~> 3.2.0)
       rspec-expectations (~> 3.2.0)
       rspec-mocks (~> 3.2.0)
-    rspec-core (3.2.2)
+    rspec-core (3.2.3)
       rspec-support (~> 3.2.0)
-    rspec-expectations (3.2.0)
+    rspec-expectations (3.2.1)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.2.0)
     rspec-mocks (3.2.1)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.2.0)
     rspec-support (3.2.2)
-    rubocop (0.29.1)
+    rubocop (0.31.0)
       astrolabe (~> 1.3)
-      parser (>= 2.2.0.1, < 3.0)
+      parser (>= 2.2.2.1, < 3.0)
       powerpack (~> 0.1)
       rainbow (>= 1.99.1, < 3.0)
       ruby-progressbar (~> 1.4)
     ruby-progressbar (1.7.5)
-    simplecov (0.9.2)
+    simplecov (0.10.0)
       docile (~> 1.1.0)
-      multi_json (~> 1.0)
-      simplecov-html (~> 0.9.0)
-    simplecov-html (0.9.0)
+      json (~> 1.8)
+      simplecov-html (~> 0.10.0)
+    simplecov-html (0.10.0)
     term-ansicolor (1.3.0)
       tins (~> 1.0)
     thor (0.19.1)
     thread_safe (0.3.5)
-    tins (1.3.5)
+    tins (1.5.1)
     unf (0.1.4)
       unf_ext
-    unf_ext (0.0.6)
+    unf_ext (0.0.7.1)
 
 PLATFORMS
   ruby
 
 DEPENDENCIES
   codeclimate-test-reporter
-  colorize
+  colorize (>= 0.7.7)
   coveralls
-  github_api
-  rake
+  github_api (>= 0.12.3)
+  rake (>= 10.4.2)
   rspec
   rubocop
   simplecov
diff --git a/lib/github_changelog_generator/fetcher.rb b/lib/github_changelog_generator/fetcher.rb
index 54533e5..e5d451c 100644
--- a/lib/github_changelog_generator/fetcher.rb
+++ b/lib/github_changelog_generator/fetcher.rb
@@ -8,21 +8,22 @@ module GitHubChangelogGenerator
   # fetcher = GitHubChangelogGenerator::Fetcher.new options
   class Fetcher
     PER_PAGE_NUMBER = 30
+    CHANGELOG_GITHUB_TOKEN = "CHANGELOG_GITHUB_TOKEN"
     GH_RATE_LIMIT_EXCEEDED_MSG = "Warning: GitHub API rate limit (5000 per hour) exceeded, change log may be " \
         "missing some issues. You can limit the number of issues fetched using the `--max-issues NUM` argument."
 
     def initialize(options = {})
       @options = options
 
-      @user = @options[:user]
-      @project = @options[:project]
-      @github_token = fetch_github_token
-      @tag_times_hash = {}
-
       @logger = Logger.new(STDOUT)
       @logger.formatter = proc do |_severity, _datetime, _progname, msg|
         "#{msg}\n"
       end
+
+      @user = @options[:user]
+      @project = @options[:project]
+      @github_token = fetch_github_token
+      @tag_times_hash = {}
       github_options = { per_page: PER_PAGE_NUMBER }
       github_options[:oauth_token] = @github_token unless @github_token.nil?
       github_options[:endpoint] = options[:github_endpoint] unless options[:github_endpoint].nil?
@@ -40,7 +41,7 @@ module GitHubChangelogGenerator
     #
     # @return [String]
     def fetch_github_token
-      env_var = @options[:token] ? @options[:token] : (ENV.fetch "CHANGELOG_GITHUB_TOKEN", nil)
+      env_var = @options[:token] ? @options[:token] : (ENV.fetch CHANGELOG_GITHUB_TOKEN, nil)
 
       unless env_var
         @logger.warn "Warning: No token provided (-t option) and variable $CHANGELOG_GITHUB_TOKEN was not found.".yellow
diff --git a/spec/unit/fetcher_spec.rb b/spec/unit/fetcher_spec.rb
new file mode 100644
index 0000000..709563f
--- /dev/null
+++ b/spec/unit/fetcher_spec.rb
@@ -0,0 +1,36 @@
+describe GitHubChangelogGenerator::Fetcher do
+  VALID_TOKEN = "0123456789abcdef"
+  before(:all) do
+    @fetcher = GitHubChangelogGenerator::Fetcher.new
+  end
+
+  describe "#fetch_github_token" do
+    token = GitHubChangelogGenerator::Fetcher::CHANGELOG_GITHUB_TOKEN
+    context "when token in ENV exist" do
+      before { stub_const("ENV", ENV.to_hash.merge(token => VALID_TOKEN)) }
+      subject { @fetcher.fetch_github_token }
+      it { is_expected.to eq(VALID_TOKEN) }
+    end
+    context "when token in ENV is nil" do
+      before { stub_const("ENV", ENV.to_hash.merge(token => nil)) }
+      subject { @fetcher.fetch_github_token }
+      it { is_expected.to be_nil }
+    end
+    context "when token in options and ENV is nil" do
+      before do
+        stub_const("ENV", ENV.to_hash.merge(token => nil))
+        @fetcher = GitHubChangelogGenerator::Fetcher.new(token: VALID_TOKEN)
+      end
+      subject { @fetcher.fetch_github_token }
+      it { is_expected.to eq(VALID_TOKEN) }
+    end
+    context "when token in options and ENV specified" do
+      before do
+        stub_const("ENV", ENV.to_hash.merge(token => "no_matter_what"))
+        @fetcher = GitHubChangelogGenerator::Fetcher.new(token: VALID_TOKEN)
+      end
+      subject { @fetcher.fetch_github_token }
+      it { is_expected.to eq(VALID_TOKEN) }
+    end
+  end
+end