text: Title: Check support for Django 1.11
  Body: Django 1.11 is now out.
  
  factory_boy should be compatible out of the box, but this still needs checking.
  
  Steps to follow:
  1. Add Django 1.11 to https://github.com/FactoryBoy/factory_boy/blob/master/tox.ini
  2. Replace Django 1.10 with Django 1.11 in https://github.com/FactoryBoy/factory_boy/blob/master/.travis.yml
  3. Make a pull request, wait for the travis build, and check that it's still working.
  
  Bonus ideas:
  - Drop support for Django 1.7 at the same time ;
  - Check for Django deprecation warnings, and see if it's possible to not trigger them without breaking support for Django 1.8/1.9/1.10 (Beware: the travis build only tests for the latest Django version).