Fix broken link
Merge pull request #125 from mozillazg/patch-1

Fix broken link
Fix interaction between `db` and `transaction_db` fixtures

This adds a new helper method (`_django_db_fixture_helper`), which is
being called from `db` and `transaction_db`.

The intermediate helper function (in contrast to using an internal fixture)
is necessary for setting up the `django_db` mark.

Fixes https://github.com/pelme/pytest_django/issues/126
doc: reviewed contributing.rst, mention "make test"
Remove accidentally committed .Python symlink