[WIP] Collection option in route under resource

Still a WIP. Not yet ready for merge
@gjaldon Yes, your understanding is correct. I think what's happening here is this:

```elixir
       resources "/comments", CommentController do
         get "/special", CommentController, :special
         get "/favorites", CommentController, :favorites, collection: true
       end
```
get "/favorites" would map to the show action based on precedence. As far phoenix is concerned, these are show matches:

```
GET "users/123
GET "users/favorites
```

"favorites" is being picked up as the id. To support a `collection` style match, we'd need to generate the clauses before the `get "/users/:id"` routes.