Folders for search in

Should we configure folders, where trailing whitespaces search should be performed in? For example, we could have `*.scss.erb` files in stylesheets folder and want to exclude it from search. What about [this way](http://rarlindseysmash.com/posts/config-and-generators-in-gems?utm_source=rubyweekly&utm_medium=email) ?

No files, tests, or entry points are named. Start by reviewing the repository structure and locating the trailing-whitespace search and configuration entry points; done should mean users can configure folders to exclude, with coverage for the example stylesheet path.

Written by the indexing model from the issue text.