[manual] Use ujson instead of simplejson.

This saves something like 15ms on our 1000 message get_old_messages
queries, and will save even more when we start sending JSON dumps into
our memcached system.

We need to install python-ujson on servers and dev instances before
pushing this to prod.

(imported from commit 373690b7c056d00d2299a7588a33f025104bfbca)

zephyr/context_processors.py

@@ -1,7 +1,7 @@
 from __future__ import absolute_import
 
 from django.conf import settings
-import simplejson
+import ujson
 
 def add_settings(request):
     return {
@@ -11,5 +11,5 @@ def add_settings(request):
 def add_metrics(request):
     return {
         'mixpanel_token': settings.MIXPANEL_TOKEN,
-        'enable_metrics': simplejson.dumps(settings.DEPLOYED),
+        'enable_metrics': ujson.dumps(settings.DEPLOYED),
     }