Add `*.styl` to built-in finders' ignore patterns

Correct staticfiles imports

the `staticfiles` module is inside `django.contrib`

Fix documentation typo in Usage section

Update link to coffeescript page and smaller typo.

'zip' in GZIPMixin should be capitalized

Update storages.rst

Typo in docs

don't fail on finders without storages attribute

check path first

PipelineStorage.listdir short-circuit returning the first match only

check if path is exists