docs($cookies): add info about angular-cookies.js

per the [top comment here](http://docs.angularjs.org/api/ngCookies.$cookies#comment-912064775)

updating documentation so it matches [$resource](http://docs.angularjs.org/api/ngResource.$resource)
and instructs the user to include the `angular-cookies.js` and load `ngCookies`.

Closes #3607

Author: robdodson

src/ngCookies/cookies.js

@@ -18,6 +18,17 @@ angular.module('ngCookies', ['ng']).
    * Only a simple Object is exposed and by adding or removing properties to/from
    * this object, new cookies are created/deleted at the end of current $eval.
    *
+   * # Installation
+   * To use $cookies make sure you have included the `angular-cookies.js` that comes in Angular
+   * package. You can also find this file on Google CDN, bower as well as at
+   * {@link http://code.angularjs.org/ code.angularjs.org}.
+   *
+   * Finally load the module in your application:
+   *
+   *        angular.module('app', ['ngCookies']);
+   *
+   * and you are ready to get started!
+   *
    * @example
    <doc:example>
      <doc:source>