Updates rubocop to ~> 0.23.0
Merge pull request #3 from jeroenj/rubocop-0.23

Updates rubocop to ~> 0.23.0
Bump version to 0.2.4
Don't process excluded files, fixes #4

This introduces another dependency on RuboCop API. Something that can't
be avoided at this point, but doesn't make me entirely happy.
Bump version to 0.2.5
Clean up Rakefile
Change Travis CI ruby version from 2.1.0 to 2.1.1
Make dependencies less pessimistic
Add .rubocop.yml and clean up some of the warnings
Merge remote-tracking branch 'upstream/master'