Add test for path conflicts
Put the original path at the end in get_possible_paths

Make it try all the combinations of prefixes and suffixes first,
and then try the original path. This way if there is a directory
named the same as our file, but without the extension and/or
prefix, we don't try to open it and avoid raising IOError.

Fixes #10.
Merge branch 'reorder-possible-paths' of https://github.com/deshipu/django-pyscss

* 'reorder-possible-paths' of https://github.com/deshipu/django-pyscss:
  Put the original path at the end in get_possible_paths
  Add test for path conflicts

Closes #13