Related to https://groups.google.com/forum/?fromgroups=#!topic/django-oscar/fscCRn4OlOg

Thanks Patryk for the tip.

Fixes #310

Fixes #308

Also update testing docs to show spec output.

Update makefile and docs to reflect this change.

Fix requirements_oscar.{py,txt} file extension in tutorial.

This makes it much easier to get started when contributing.  The docs
are also updated.

This makes it much easier to get started when contributing.  The docs
are also updated.

This avoids conflicts with other libraries that use the same trick for
extending templates.

This syncs the documentation with the 'vanilla' example