docs(angular.module): improve docs

it wasn't clear before that if given the same name a second time this method RETRIEVES an EXISTING module.  Not even sure if my description is accurate, hoping someone will either confirm and merge or clear it up.

Closes #3666

Author: Sequoia

src/loader.js

@@ -23,10 +23,13 @@ function setupModuleLoader(window) {
      * @name angular.module
      * @description
      *
-     * The `angular.module` is a global place for creating and registering Angular modules. All
-     * modules (angular core or 3rd party) that should be available to an application must be
+     * The `angular.module` is a global place for creating, registering and retrieving Angular modules.
+     * All modules (angular core or 3rd party) that should be available to an application must be
      * registered using this mechanism.
      *
+     * When passed two or more arguments, a new module is created.  If passed only one argument, an
+     * existing module (the name passed as the first argument to `module`) is retrieved.
+     *
      *
      * # Module
      *