make it work with non-contrib version of staticfiles

pipeline/finders.py

-from django.contrib.staticfiles.finders import BaseStorageFinder
+try:
+    from django.contrib.staticfiles.finders import BaseStorageFinder
+except ImportError:
+    from staticfiles.finders import BaseStorageFinder
 
 from pipeline.storage import PipelineStorage
 

pipeline/storage.py

-from django.contrib.staticfiles import finders
-from django.contrib.staticfiles.storage import CachedStaticFilesStorage, StaticFilesStorage
+try:
+    from django.contrib.staticfiles import finders
+    from django.contrib.staticfiles.storage import CachedStaticFilesStorage, StaticFilesStorage
+except ImportError:
+    from staticfiles import finders
+    from staticfiles.storage import CachedStaticFilesStorage, StaticFilesStorage
 from django.core.exceptions import ImproperlyConfigured
 from django.core.files.storage import get_storage_class
 from django.utils.functional import LazyObject

pipeline/templatetags/compressed.py

+try:
+    from django.contrib.staticfiles.storage import staticfiles_storage
+except ImportError:
+    from staticfiles.storage import staticfiles_storage
 from django import template
-from django.contrib.staticfiles.storage import staticfiles_storage
 from django.template.loader import render_to_string
 
 from pipeline.conf import settings