Update tests due to new django releases

Hello.
this it's just a small update to django-leaflet tests:
 - add support for Python 3.4
 - add support for Django 1.7
 - drop support for Django 1.5 (it's a unsupported release now)
 - add support fo sqlite and python3.x (no need for pysqlite)
 - fix tests for Django dev

Feel free to squash all my commits in one.

Cheers
Marco