Bump djangorestframework from 3.7.3 to 3.7.7 in /backend/uclapi
Bump djangorestframework from 3.7.3 to 3.7.7 in /backend/uclapi

Bumps [djangorestframework](http://www.django-rest-framework.org) from 3.7.3 to 3.7.7.
uclapi/uclapi,uclapi/uclapi,uclapi/uclapi,uclapi/uclapi