Allow base_url to be overridden

dj_static.py

@@ -34,12 +34,12 @@ class Cling(WSGIHandler):
     """WSGI middleware that intercepts calls to the static files
     directory, as defined by the STATIC_URL setting, and serves those files.
     """
-    def __init__(self, application, base_dir=None, ignore_debug=False):
+    def __init__(self, application, base_dir=None, base_url=None, ignore_debug=False):
         self.application = application
         self.ignore_debug = ignore_debug
         if not base_dir:
             base_dir = self.get_base_dir()
-        self.base_url = urlparse(self.get_base_url())
+        self.base_url = urlparse(base_url or self.get_base_url())
 
         self.cling = static.Cling(base_dir)
         try: