Delay import of sqlalchemy_filters project

since apparently we can't use this (and hence our new API) unless python3

tailbone/api/master.py

@@ -26,8 +26,6 @@ Tailbone Web API - Master View
 
 from __future__ import unicode_literals, absolute_import
 
-from sqlalchemy_filters import apply_sort, apply_pagination
-
 from tailbone.api import APIView, api
 from tailbone.db import Session
 
@@ -66,6 +64,8 @@ class APIMasterView(APIView):
         return '{}s'.format(cls.get_object_key())
 
     def _collection_get(self):
+        from sqlalchemy_filters import apply_sort, apply_pagination
+
         cls = self.get_model_class()
         query = self.Session.query(cls)
         context = {}