Use Python native JSON library instead of Django's

mayan/apps/installation/classes.py

@@ -1,6 +1,7 @@
 from __future__ import absolute_import
 
 from collections import namedtuple
+from json import dumps
 import os
 
 import pbs
@@ -12,7 +13,6 @@ except pbs.CommandNotFound:
     PIP = False
 
 from django.conf import settings
-from django.utils.simplejson import dumps
 
 
 class PIPNotFound(Exception):