Added msg.isMentioned

lib/Structures/Message.js

@@ -37,6 +37,15 @@ var Message = (function () {
 		});
 	}
 
+	Message.prototype.isMentioned = function isMentioned(user) {
+		user = this.client.internal.resolver.resolveUser(user);
+		if (user) {
+			return this.mentions.has(user);
+		} else {
+			return false;
+		}
+	};
+
 	Message.prototype.toString = function toString() {
 		return this.content;
 	};