[1.7.x] Documented Context.get() method.
[1.7.x] Documented Context.get() method.

Backport of 4d9414098bd98aacd241827a01f6ad2dff71f113 from master

oscaro/django,jyotsna1820/django,jyotsna1820/django,jyotsna1820/django,oscaro/django,oscaro/django,jyotsna1820/django,oscaro/django