Upgrade Django to 1.4.22

https://www.djangoproject.com/weblog/2015/aug/18/security-releases/

Upgrade Django to 1.4.22
c3234c1c · Ned Batchelder · 8e35fc67 · c3234c1c
Commit c3234c1c authored 9 years ago by Ned Batchelder
--- a/requirements/edx/base.txt
+++ b/requirements/edx/base.txt
@@ -34,7 +34,7 @@ django-storages==1.1.5
 django-threaded-multihost==1.4-1
 django-method-override==0.1.0
 djangorestframework==2.3.14
-django==1.4.21
+django==1.4.22
 elasticsearch==0.4.5
 facebook-sdk==0.4.0
 feedparser==5.1.3