We've got all of the documentation (and source code) for all versions of Ruby, and all versions of all Ruby gems over at Omniref: http://www.omniref.com
Yeah, Omniref is really cool. We're going to release our Ruby analyzer soon as a standalone open-source tool. If you are interested in using it to get semantically annotated code on Omniref, let me know (we'd prioritize Ruby over some of the other language analyzers we are also going to release).
Some examples:
https://www.omniref.com/ruby/2.1.2/symbols/Enumerable/sort_b...
https://www.omniref.com/ruby/gems/sass/3.3.8
https://www.omniref.com/ruby/2.1.2/symbols/MiniTest
https://www.omniref.com/ruby/gems/activerecord/4.1.1/symbols...
You can even build custom search engines for your project by uploading your project's Gemfile.