A few caching optimizations to go.py
A few caching optimizations to go.py

Feature processing is slightly less of a bottleneck

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