Add username() method

Author: juho05

src/main/java/org/codegame/client/GameSocket.java

@@ -83,7 +83,7 @@ public void connect(String gameId, String playerId, String playerSecret) throws
 		}
 	}
 
-	public void connect(String gameId) throws IOException {
+	public void spectate(String gameId) throws IOException {
 		if (session.gameURL != "")
 			throw new IllegalStateException("This socket is already connected to a  game.");
 
@@ -169,6 +169,14 @@ public void removeCallback(String eventName, String id) {
 		eventListeners.get(eventName).callbacks.remove(id);
 	}
 
+	public String username(String playerID) throws IOException {
+		if (usernameCache.containsKey(playerID))
+			return usernameCache.get(playerID);
+		var username = api.fetchUsername(session.gameId, playerID);
+		usernameCache.put(playerID, username);
+		return username;
+	}
+
 	public Api getApi() {
 		return api;
 	}