Ignore output directory.

Split from:

Commit: b7d3fa139d60c4d049552bfefe2fb3141b414e2a
Author: CJ Carey <perimosocordiae@gmail.com>
Date:   Sat Jul 20 05:17:53 2013 -0400
Exit with a warning if hlint isn't available.

Split from:

Commit: b7d3fa139d60c4d049552bfefe2fb3141b414e2a
Author: CJ Carey <perimosocordiae@gmail.com>
Date:   Sat Jul 20 05:17:53 2013 -0400

Closes #48