Abort any pending async requests for models and collections

Fixes #3360.
Make code reusable by external app
Cleanup: PEP8
Webpack: use local installation

It's a project's dev dependency after all, and way more easier to manage
and control.
Travis: port travis config from stable/2.6.0
requirments: ensure pyDes installs
docs: fix links
Travis: allow doc warnings until docs review is complete

Once #3307 is complete this should be dropped.
Makefile: add pep8 command
Travis: bump Django to 1.6.5 add 1.7.1
Travis: disable migration testing

Bring this back once we have a migration path from older versions.
Travis: force MyISAM

At least until we close #3363 and #3364