Support for .jscsrc files

Adding support for using `.jscsrc` as the default config file value, while still falling back to .jscs.json for now. Once we decide we no longer care about the json file this codepath can be massively simplified back to what it was.

I broke it out into its own module to ease testing, as currently testing the CLI is kinda dodgy for me on Windows (see #144). Also the existing CLI path doesn't provide a way to override the default `process.cwd()` value which is necessary for this sort of code to be properly tested.

Fixes #196