Add a formatter for ruby

[fowles]

https://github.com/erniebrodeur/ruby-beautify

[dbarnett]

Someone also suggested rubocop in http://www.reddit.com/r/vim/comments/2uab1g/codefmt_a_plugin_for_formatting_code_using/co9pn5e. Wonder how it compares to ruby-beautify…

[fowles]

The --auto-correct option is marked experimental for robocop.

https://github.com/bbatsov/rubocop

[zinovyev]

I think that rubocop is somehow like an industry standard nowadays. So implementing a plugin for it would be a good deed :)