Update controllers.md

Suggest not describing the `Route::controller` method as RESTful or listing it under the "RESTful Controllers" heading.

REST 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, for example a User or a Tag.
+ 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`.