Update _compat.py

Support both __builtins__ as a dictionary and a module.

flask_admin/_compat.py

@@ -49,7 +49,7 @@ else:
         return unicode(s)
 
     # Helpers
-    reduce = __builtins__.reduce
+    reduce = __builtins__['reduce'] if isinstance(__builtins__, dict) else __builtins__.reduce
     from urlparse import urljoin