RubyForge is no more. Docs can be found on rdoc.info
Merge pull request #534 from adelcambre/update-doc-link

RubyForge is no more; replace the reference to it in the README.md with a reference to rubydoc.
Update Travis with newer Rubies 2.0, 2.1, 2.2, rbx
Merge pull request #550 from sodabrew/travis_new_rubies

Update Travis with newer Rubies 2.0, 2.1, 2.2, rbx