Add username field to user info.

Most of the networks don't allow unicode username. This patch allows users to specify username optionally. When specified, username is used for connecting IRC networks instead of nickname.

src/client.js

@@ -138,6 +138,7 @@ Client.prototype.connect = function(args) {
 	});
 
 	var nick = args.nick || "shout-user";
+	var username = args.username || nick;
 	var realname = args.realname || "Shout User";
 
 	var irc = slate(stream);
@@ -148,7 +149,7 @@ Client.prototype.connect = function(args) {
 
 	irc.me = nick;
 	irc.nick(nick);
-	irc.user(nick, realname);
+	irc.user(username, realname);
 
 	var network = new Network({
 		host: server.host,

users/example/user.json

@@ -9,6 +9,7 @@
 		"tls": true,
 		"password": "serverpw",
 		"nick": "john",
+		"username": "john",
 		"realname": "John Doe",
 		"commands": [
 			"/msg NickServ identify password",