Allowing @import of paths relative to each stylesheet

In this change, I've added the directory of each stylesheet to the parser paths, allowing `@import` of files relative to each stylesheet.

In our application, we found it useful to be able to `@import` either our own custom variables/mixins or those of a library like Bootstrap. I understand that this is entirely "unorthodox" in the context of a component, but in the scope of a larger application, I'm sure this is generally useful.