Display proper IGN of players

[BattleMage0231]

Currently, the application will display the given name of the player to stalk in its output message. However, the given name isn't always the proper IGN of the player (the capitalization could be different).

When calling the Mojang API to get a player's UUID, the returned JSON conveniently also contains their proper name.

If this feature is implemented, caching must also be changed to allow usernames to be cached.