do not ignore 'False' connection settings (fixes #127)

Author: Len Buckens

flask_mongoengine/__init__.py

@@ -31,7 +31,7 @@ def _create_connection(conn_settings):
             connections[conn.get('alias')] = _create_connection(conn)
         return connections
 
-    conn = dict([(k.lower(), v) for k, v in conn_settings.items() if v])
+    conn = dict((k.lower(), v) for k, v in conn_settings.items() if v is not None)
 
     if 'replicaset' in conn:
         conn['replicaSet'] = conn.pop('replicaset')