Reducing scope of test to only test rebuilding partial

Planning on matching the first .sass or .scss that matches the path and partial name
Testing the ability to replace the underscore
Inserting an underscore to the right place in a string
Being explicit about the ability to find the partial in multiple levels of nesting.
Renaming module for clarity
Cleaning up unnessassary self
Making method private because it is only needed for this module
Moving method into tools, since it is needed in several places
Moving test into correct spec