Merge pull request #1 from Wilduck/master

Distinguish between global and matrix environment variables.
Update .travis.yml

Only test for Django 1.6 out of the box
Update setup.py

All new packages default to requiring Django 1.6 or above
Update .travis.yml

Updated travis.yml to use different style for running pyflakes and pep8
Update run_tests.py

Added a comment to explain the reasoning of importing django nose after settings configuration
Update .travis.yml

Added flake8 as the checker for Travis.yml
Update README.md