Option to use locally installed sass-lint

[bensleveritt]

Not hit any major issues yet, but it would be nice to have an option to use the locally installed sass-lint, to ensure I have the same linter as my team and CI system.

This would be similar to how linter-eslint works.

[Twintails]

.sass-lint.yml included in the project root folder works for me. I believe it was recently fixed as there was another bug report on it which has been closed #173