The idea of splitting integration from unittests is good in theory
but leads to a lot of mental overhead. Besides whenever a tests
interacts with a database it isn't a unittest anyway.

Better to use filenames which are commonly used in the python word then
custom ones.

The test suite brings it's own stock record model for testing. Django
1.7 requires that we only import models from apps in INSTALLED_APPS, so
we need to use it to avoid clashes.

It only contains importers. Also added comments about their usage,
or lack thereof.

Naming it like a built-in exception makes it hard to distinguish between
the two and is error prone.

This allows updating code in both places, if necessary. Getting Django
1.5 support would be painful otherwise. This also removes the circular
dependency of django-oscar-testsupport on Oscar.

The requirements were merged. The imports were updated
accordingly. Unused imports in the touched files were removed. No
further changes.

Fixes #376

Also split them into unit and functional tests.

Now they are always available within the oscar app.