assertHttpAccepted produces better error message
Merge pull request #1047 from damoti/master

assertHttpAccepted produces better error message
Documented that tests can be run with tox

Also noted that tests may not *always* pass with development versions
of Django.

Closes #1048 and closes #857.
Removed py26-dev tox environment

This was missed in commit 4320db4ac, I believe.

Closes #312.