**DNM** Notify matching askers model field

**DO NOT MERGE**

https://github.com/groovecoder/codesy/commit/27ef1a6e7183f504e9828916fa2493845d564162 put me into a race condition - saving the `notified` field value sends another `post_save` signal which, although it could work this way, feels very, very wrong. (And hard to test.)

I think we should probably add http://django-notification.readthedocs.org/en/latest/ instead?