Ignore that the Collection already exists in devel

The app is remounted a lot – of course the collection already exists.
So don't tell me about it.
General Code Review

* JSLint :wink:
* Some tiny JavaScript quirks
* Tiny improvements (usage of `Underscore#map`'s bind)
* Introduction of a Model (was a fake beforehand :wink:)
* Fixed the error output of the `put` route