Fix race conditions on submission edit

[nightsh]

Let's have two users are logged in on different systems, simultaneously.

Supposing they can both edit one submission, once one of them saves the model, the other won't see it until a page refresh / model acquiring phase, causing a complete overwrite of the other's modifications.

See #34 - this is caused by Ember Data not reloading its models. If the models would be populated entirely by API calls, the problem would be a lot easier to fix.