Emacs and unix integration

[jonas054]

Rubocop looks like a really nice framework where it will be relatively easy to add more and more functionality. My first wish is to make it integrate better with the Unix command line and with Emacs compilations and flymake.

In this branch I have implemented:

• Possibility to call "rubocop file.rb" and "rubocop *.rb" (only "rubocop" and "rubocop *.rb" was supported in master).
• An option -e/--emacs that outputs on a format suitable for compilation buffers and flymake.

[bbatsov]

Great additions! Thanks!