Rephrase handling of TEST_DB_NAME with ':memory:'
Merge the test clients environ setup from Django master

I have noticed and compared it because of flake8 issues, and the only
non-whitespace changes are the addition of `str()` and `b''` wrappers.
Merge pull request #152 from blueyed/merge-django-test-client

Merge client environ setup from Django master
tests: use `dedent` with `extra_settings`, indent
django_testdir: use `ensure=True` with `write` for `create_*`
Merge pull request #154 from blueyed/testdir-use-dedent

tests: use more dedent and indenting
Check QA: add tasks to run flake8 to tox/travis

Also fix any current issues.
Merge pull request #153 from blueyed/checkqa

Check QA: add flake8 to tox/travis
Remove the conftest.py PYTHONPATH hack from FAQ. Refs #23.
Added a note about pytest-pythonpath to FAQ, thanks to Alexander
Schepanovski for the suggestion. Refs #23.
Use pytest==2.6.0
tox/travis: test with both pytest 2.5 and 2.6

Fixes https://github.com/pelme/pytest_django/issues/151