Fix strange issue with ParameterValidator settings

When imported at top-level, `settings` was a Python module, rather than a Django
settings object. Not sure why.

conservancy/__init__.py

@@ -1,10 +1,8 @@
 import hashlib
 
-from django.conf import settings
-
-
 class ParameterValidator:
     def __init__(self, given_hash_or_params, params_hash_key=None):
+        from django.conf import settings
         if params_hash_key is None:
             self.given_hash = given_hash_or_params
         else: