Add 'New' link to main ideas page
Fix (multiple) issue where clicking New would barf

Okay, trying to take the training wheels off just a bit.

Running into issues with the way I did setupController.

First, I forgot to pass in the controller into the lambda.
Then, I ran into this. https://stackoverflow.com/questions/22254096/emberjs-cannot-delegate-set

Long story short, since we're not dealing with a bonafide model object, we use Controller instead of ObjectController.
Fix major design issue: New is nested under top-level Ideas, not an individual Idea

This fixes weird behaviour like:
* having a `new` url which contains the record you were just viewing (wtf)
* when clicking on `new`, not having the current record removed from display