* moves tests package to root of project and renames it to test_django_filters
* splits tests.py into multiple files
* removes fixture need by creating instances on the fly
** attempted to use factory_boy instead, but it isn't py3k compatible yet
* uses django-discover-runner to find the test cases
while primarily focused on test refactoring, it also:
* updates runtests.py to allow more flexibility when running tests
* adds a runshell.py which configures django, runs syncdb and loads the test environment shell (in-memory sqlite db)
* adds pip requirements files for new test dependencies
* updates MANIFEST.in for test package split
* uses py3k compatible relative imports when possible
* removes XMLField handling, since we only support Django >= 1.4
* removes unnecessary code to get length on MultipleChoiceField's choices when filtering
* updates code for pep8 and pyflakes adherence