Make the SASS compiler compatible with libsass-python

Use the new build env on Travis

faster vms, more ram, more cpu, better boot times, awesome network

docs coming soon

The idea is to have a process similar to collecstatic, and
copy files in a temporary directory.

This avoid storage that use finders, streamline dev process with
production process, and make compilers easier to deal with.

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.