add Plugin.env to load templates

Author: Martin Journois

folium/plugins/plugin.py

@@ -9,13 +9,17 @@
 """
 from uuid import uuid4
 
+from jinja2 import Environment, PackageLoader
+ENV = Environment(loader=PackageLoader('folium', 'templates'))
+
 class Plugin(object):
     """Basic plugin object that does nothing.
     Other plugins may inherit from this one."""
     def __init__(self):
         """Creates a plugin to append into a map with Map.add_plugin. """
         self.plugin_name = 'Plugin'
         self.object_name = uuid4().hex
+        self.env = ENV
 
     def add_to_map(self, map):
         """Adds the plugin on a folium.map object."""