docs($controller): add controllerAs definition

src/ng/controller.js

@@ -59,6 +59,9 @@ function $ControllerProvider() {
      *    * if $controllerProvider#allowGlobals, check `window[constructor]` on the global
      *      `window` object (not recommended)
      *
+     *    If use a string with `controller as` syntax, the controller instance is published into a `scope`
+     *    property, but the `scope` must be injected into `locals` param.
+     *
      * @param {Object} locals Injection locals for Controller.
      * @return {Object} Instance of given controller.
      *