Options: a class to wrap Hash-accessing options choices

- protects against bad names

lib/github_changelog_generator/parser.rb

@@ -187,7 +187,7 @@ module GitHubChangelogGenerator
 
     # @return [Hash] Default options
     def self.default_options
-      {
+      Options.new(
         tag1: nil,
         tag2: nil,
         date_format: "%Y-%m-%d",
@@ -217,7 +217,7 @@ module GitHubChangelogGenerator
         http_cache: true,
         cache_file: "/tmp/github-changelog-http-cache",
         cache_log: "/tmp/github-changelog-logger.log"
-      }
+      )      
     end
 
     # If `:user` or `:project` not set in options, try setting them