We need some way check if tags have been fetched then run some code immediately/when they've been fetched.
My thought was to use jquery promise objects (which is what we already get back from a ```.ajax()``` call or ```.fetch()``` )..
So we can do something like ```TagsCollection.fetched.done(function() { // do stuff });```
However better would be if it does something a little smarter like
```TagsCollection.initialFetch.done()``` where that would always return a promise object, but also trigger the fetch() call if needed.