RPS Server and some test clients
Tests cover:
- Trying to sign up multiple times in a row without playing
- Multiple pairs sign up before they play
- Trying to play without signing up
- Opponent quitting before other player plays
- Opponent quitting after other player plays
- Player sending empty play request (can recover with correct play)
- Player sending invalid play request (can recover with correct play)
- Make sure correct player wins
- Quitting before playing anything