Fine-tune nested naming conventions

We no longer create nested namespaces. This
was clobbering models in some cases. For
example, if you had a nested "comments" inside
of a "post" route, in would create
App.Post.CommentRoute—nuking the App.Post
model.

The new rules for naming are simple:

**Controllers and Routes**
`App.ParentCurrentController`
`App.ParentCurrentRoute`

**Templates**
`parent/current.handlebars`
**Models**
`App.Current`

For example:

```js
App.Router.map(function(match) {
  match('/:post_id').to('post', function(match) {
    match('/comments').to('comments');
  });
});
```

The nested comment route would map to the
following:

```js
App.PostCommentsController
App.PostCommentsRoute
post/comments.handlebars
App.Post
```