Remove use of rubygems
Merge pull request #317 from troessner/remove-rubygems

Remove use of rubygems from env.rb
Work around broken Open3 on JRuby 1.7.16
Add JRuby and Rubinius to Travis CI config
Allow any Ruby 2.1 on Travis CI
Merge pull request #320 from troessner/issue-support-more-rubies

Support more rubies
ModuleInitialize smell - having initialize in mixin is bad idea