Add results caching
Minor improvements
Merge branch 'cache' of github.com:runk/coffeelint into runk-cache
--cache is boolean only, not configurable.

The intention was to allow --cache [/some/path] where the path is
optional. I don't see how to make it optional, it's either a boolean, or
requires a path to be specified. I think `os.tmpdir()` is safe enough to
just not make this configurable.
Merge branch 'runk-cache'