Added getvalue() to HttpResponse to return the content of the response,
along with a few other methods to partially match io.IOBase.
Thanks Claude Paroz for the suggestion and Nick Sanford for review.
Added comments in the three empty models.py files that are still needed.
Adjusted the test runner to add applications corresponding to test
labels to INSTALLED_APPS even when they don't have a models module.
Sergey Parkhomenko
Michael Kelly
Unai Zalakain
Aymeric Augustin
Jason Myers