Not caching the creation of a cursor

[jandebleser]

This gives problems if you have more than 1 connection in your DATABASES variable in settings.py. The cursor will be closed and give a "cursor already closed" error.

[maxtepkeev]

Hi @jandebleser

I didn't know this problem exists, thanks for raising this issue and thanks for the PR.

Unfortunately tests don't pass, have a look at travis for details (don't look at Python 2.6 failures, they aren't connected with your PR)

[jandebleser]

I fixed the tests and I think it looks ok now.