Update to Rubocop 0.28.0
Merge pull request #784 from intridea/rubocop-0.28.0

Update to Rubocop 0.28.0
Adding Ruby 2.2 to the Travis CI test matrix
Merge pull request #783 from intridea/travis-ruby-22

Adding Ruby 2.2 to the Travis CI test matrix
Merge branch 'master' of git://github.com/intridea/omniauth