Remove leading characters from paths.

Hopefully this is fine to merge in; I can't think of any use cases where it may be a breaker.

Based on this issue I had:
http://stackoverflow.com/questions/26301406/brunch-requiring-modules-outside-of-app-directory

In order to be able to require any modules that are outside Brunch's own root, I had to add `../path` to my watched files in the config. However, require doesn't seem to like the parent folder symbol (for want of a better name), so I've changed it so that it'll strip of any leading `../`s from the path.

Thoughts?
Cheers, Matt.