manager: test command should exit with same exit code as pytest
manager: simplify command names (test instead of runtests) and add help message
tests: django now uses DEFAULT_MAX_NUM (which is 1000) for the max_num in formsets by default.

Apparently this was added in a minor version of 1.4.x and I was testing
against a old 1.4.3 instead of the latest 1.4.10

Only affects my tests
tests: ensure media_root is clean before tests
tests: move asserts to separate file
tests: run tests using tox

Only testing on py2.6 and 2.7 and django 1.4 and 1.5. Initial run on django 1.6
showed some issues that need to be fixed, it\'s not working on 1.6 yet.

Didn't test on py3 yet