add webhooks v8 (#759)

* add webhook structure and getChannelWebhooks as well as getServerWebhooks

* add sendMessage

* add the ability to edit create and delete hooks

* remove server wide cache and add getter.

lib/Structures/Server.js

@@ -450,6 +450,20 @@ var Server = (function (_Equality) {
 	};
 
 	_createClass(Server, [{
+		key: "webhooks",
+		get: function get() {
+			return this.channels.map(function (c) {
+				return c.webhooks;
+			}).reduce(function (previousChannel, currentChannel) {
+				if (currentChannel) {
+					currentChannel.forEach(function (webhook) {
+						previousChannel.add(webhook);
+					});
+				}
+				return previousChannel;
+			}, new _UtilCache2["default"]("id"));
+		}
+	}, {
 		key: "createdAt",
 		get: function get() {
 			return new Date(+this.id / 4194304 + 1420070400000);

lib/Structures/TextChannel.js

@@ -30,6 +30,7 @@ var TextChannel = (function (_ServerChannel) {
 
 		this.topic = data.topic;
 		this.lastMessageID = data.last_message_id || data.lastMessageID;
+		this.webhooks = new _UtilCache2["default"]("id");
 		this.messages = new _UtilCache2["default"]("id", client.options.maxCachedMessages);
 	}