Fixed DjangoFilterBackend not returning a query set.

Fixed bug unveiled in #682.

Signed-off-by: Kevin Stone <kevinastone@gmail.com>
Added unit test for failing DjangoFilterBackend on SingleObjectMixin that was resolved in b10663e02408404844aca4b362aa24df816aca98

Signed-off-by: Kevin Stone <kevinastone@gmail.com>
Removed pagination regression special case for Django<1.4.   Having DjangoFilterBackend return an actual query set fixes this issue.

Signed-off-by: Kevin Stone <kevinastone@gmail.com>
Merge pull request #768 from kevinastone/master

Fixeds DjangoFilterBackend Incompatibility with SingleObjectMixin