PrettyPrint class is included using lowercase 'pp'

lib/github_changelog_generator/parser.rb

@@ -1,6 +1,6 @@
 #!/usr/bin/env ruby
 require 'optparse'
-require 'PP'
+require 'pp'
 require_relative 'version'
 
 module GitHubChangelogGenerator
@@ -94,4 +94,4 @@ module GitHubChangelogGenerator
       options
     end
   end
-end
+end