Added development versions of django 1.7 to tox config.

Signed-off-by: Kevin Stone <kevinastone@gmail.com>
Disabled django 1.7 due to error between nose runner and app loader.

Signed-off-by: Kevin Stone <kevinastone@gmail.com>
Updated travis config to build against multiple django versions.

Signed-off-by: Kevin Stone <kevinastone@gmail.com>