PipelineFinder.list should always return empty list

Add missing ignore_pattern to FileSystemFinder.

Include quotes in NON_REWRITABLE_URLS

Added sophicware to the list.

Remove tempdir storage location

Make the SASS compiler compatible with libsass-python

https://github.com/cyberdelia/django-pipeline/issues/394

TL;DR Setting a default location like this causes breakage and isn't the
responsibility of `PipelineMixin`

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