Rename Overload to Override

We should rename `overload` to `override` since it is more accurate.

From the [PHP.net](http://php.net/manual/en/language.oop5.overloading.php):

> Overloading in PHP provides means to dynamically "create" properties and methods. These dynamic entities are processed via magic methods one can establish in a class for various action types.

> The overloading methods are invoked when interacting with properties or methods that have not been declared or are not visible in the current scope.

Overriding is a more accurate technical term in this case since we're not dealing with the magic methods `__set`, `__get`, `__isset`, `__unset`.

Props for the original patch by @emiluzelac