Added Gitter badge
Merge pull request #3 from gitter-badger/gitter-badge

Add a Gitter chat badge to README.md
Updated project Ruby version and gemset and added JRuby head to Travis along with newer versions of Ruby 2.1.x
Merge branch 'master' of github.com:ruby-odata/odata
Merge branch 'master' into feature/represent_metadata_as_hash