Update vendor to latest.

Pulls in the following (merge commits removed):

91561d9 Update to Django 1.4.6  r=r1cky
e8e6095 Update tower
963f25c upgrade django-session-csrf for safer keys
ba468e6 upgrading django-session-csrf to avoid possible MemcachedKeyLengthError, r=Osmose
9327312 Update funfactory
1bdbc40 Update django-multidb-router to ignore .pycs
d5db036 Drop django-arecibo.
3fab887 Upgrade commonware to 0.4.2
f23dc06 update requests to 1.1.0

The Django update is the one we really care about.