Replace simpljson imports with json

This has been in standard python since 2.6, and we don't really care
about supporting anything older than that (even our old and soon to
be upgraded environments use 2.7)

pgweb/lists/views.py

@@ -3,7 +3,7 @@ from django.http import HttpResponse
 from django.views.decorators.csrf import csrf_exempt
 from django.conf import settings
 
-import simplejson as json
+import json
 
 from pgweb.util.contexts import NavContext
 from pgweb.mailqueue.util import send_simple_mail