Respect scss-lint config files

Now that `scss-lint` supports config file loading, we need to match
the behavior of the `RubyStyle` pre-commit check and make sure that the
appropriate configuration file is passed to `scss-lint` for a given
file.

Change-Id: Ie451ae9c782418ff23f1243fca94c3aff7489d7b
Reviewed-on: https://gerrit.causes.com/31580
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>