Update controllers.md

Suggest not describing the `Route::controller` method as RESTful or listing it under the *RESTful Controllers* heading.

REST generally has the following three criteria:
+ You have a standard set of URLs to perform basic CRUD operations on a Resource.
+ A Resource is some entity of your application.
+ Every Resource has a unique ID.

None of those things are being enforced when using `Route::controller`.

A more appropriate name for this heading might be *Implicit Routing*; you're mapping routes to a Controller without explicitly defining those routes. There's nothing RESTful about this.

The method that comes after, `Route::resource`, falls more into the category of RESTful routing. So perhaps that heading might become `RESTful Resource Controllers`.