adds new WebhookClient and allows you to fetch channel webhooks and such without being "over the top" (#768)

* start blocking out client

* proto webhookclient

* wee working webhooks

* it's all working

* run docs

* fix jsdoc issues

* add example for webhookClient

* add example in the examples place

* fix docs

src/client/WebhookClient.js

@@ -0,0 +1,46 @@
+const Webhook = require('../structures/Webhook');
+const RESTManager = require('./rest/RESTManager');
+const ClientDataResolver = require('./ClientDataResolver');
+const mergeDefault = require('../util/MergeDefault');
+const Constants = require('../util/Constants');
+
+/**
+ * The Webhook Client
+ * @extends {Webhook}
+ */
+class WebhookClient extends Webhook {
+  /**
+   * @param {string} id The id of the webhook.
+   * @param {string} token the token of the webhook.
+   * @param {ClientOptions} [options] Options for the client
+   * @example
+   * // create a new webhook and send a message
+   * let hook = new Discord.WebhookClient('1234', 'abcdef')
+   * hook.sendMessage('This will send a message').catch(console.log)
+   */
+  constructor(id, token, options) {
+    super(null, id, token);
+
+    /**
+     * The options the client was instantiated with
+     * @type {ClientOptions}
+     */
+    this.options = mergeDefault(Constants.DefaultOptions, options);
+
+    /**
+     * The REST manager of the client
+     * @type {RESTManager}
+     * @private
+     */
+    this.rest = new RESTManager(this);
+
+    /**
+     * The Data Resolver of the Client
+     * @type {ClientDataResolver}
+     * @private
+     */
+    this.resolver = new ClientDataResolver(this);
+  }
+}
+
+module.exports = WebhookClient;