Adding test in test_gamestate demonstrating bug in GameState.copy()
Adding test in test_gamestate demonstrating bug in GameState.copy()

This bug was fixed in the previous commit.

vftens/RocAlphaGo,Rochester-NRT/AlphaGo,Rochester-NRT/AlphaGo,MaMiFreak/RocAlphaGo,Rochester-NRT/RocAlphaGo,Rochester-NRT/AlphaGo,wrongu/RocAlphaGo,hiropppe/RocAlphaGo