Perk CSS not updating properly

[alarner]

Steps to reproduce:

1. Add a new sass include file
2. Import that include file into main.scss
3. Change the include file - notice that the css doesn't update

Problem: Dependency graph not updating when import is included in main.scss because it only updates when a new file is added, not when a file is changed.

Fix: Cause the dependency graph to be rebuilt when a file is changed as well.