Fix tests by using regular six instead of branca.six (#1012)

Use regular six package instead of branca

Author: Conengmo

tests/test_features.py

@@ -10,8 +10,9 @@
 
 import os
 
+from six import text_type
+
 from branca.element import Element
-from branca.six import text_type
 
 from folium import Map, Popup
 import folium