If Rakefile is an extension, any requires are runtime deps

Gemfile

@@ -8,5 +8,4 @@ group :test do
   gem "coveralls", "~>0.8", require: false
   gem "simplecov", "~>0.10", require: false
   gem "codeclimate-test-reporter", "~>0.4"
-  gem "overcommit", "~>0.31"
 end

Gemfile.lock

@@ -4,6 +4,7 @@ PATH
     github_changelog_generator (1.10.3)
       colorize (~> 0.7)
       github_api (~> 0.12)
+      overcommit (~> 0.31)
 
 GEM
   remote: https://rubygems.org/
@@ -97,7 +98,6 @@ DEPENDENCIES
   codeclimate-test-reporter (~> 0.4)
   coveralls (~> 0.8)
   github_changelog_generator!
-  overcommit (~> 0.31)
   rake (~> 10.0)
   rspec (~> 3.2)
   rubocop (~> 0.31)

github_changelog_generator.gemspec

@@ -26,6 +26,7 @@ Gem::Specification.new do |spec|
 
   spec.add_runtime_dependency("github_api", ["~> 0.12"])
   spec.add_runtime_dependency("colorize", ["~> 0.7"])
+  spec.add_runtime_dependency("overcommit", "~>0.31")
 
   # Development only
   spec.add_development_dependency "bundler", "~> 1.7"