Implement the MasterMind game.
The computer "thinks" a string with 4 different digits. You guess which digits. For every digit that matched both in value, and in location the computer gives you a *. For every digit that matches in value, but not in space the computer gives you a +.
Try to guess the given number in as few guesses as possible.
Computer: 2153
You: 2467 *
You: 2715 *++
