Fixed #15: implemented support for django cache framework

[agateblue]

This PR adds support for django's cache framework, as described in #15.

A couple of notes:

• I've added a basic test, but this may be not enough. It's a bit complex for me to test this more thoroughly because this would require mocking and due to the wide range of supported Python versions, I don't know how to do that properly without introducing more dependencies
• I've added py34, py35 and py36 env in tox.ini
• Ive added Django to test dependencies (this is required to run the django tests)
• This implementation does not support ttl or locking. Tll is not currently doable within django (see this question for example), locking is implementable I think, I'm just not really familiar with the underlying logic.

Tell me if you need some fixes or have any question.

[mikeboers]

Thank you for this. I'll do my best to get back to this soon™. I've got a bit of a deadline in non-FLOSS work, so it might be a little longer. 😬

[agateblue]

Sure, no worries! I'll use my fork in the meantime :)

[ppwfx]

Can you merge it please? just drop support for 2.6 and 3.3

[agateblue]

I have to admit it would be useful to see this included in a real PyPi release. let me know if I can help with anything to make it easier :)

[mikeboers]

My goodness I sat on this forever, and it was just a cherry-pick away.

I'm just waiting on Travis to tell me it still passes.

[agateblue]

Awesome, thank you!