Switch to Python 3.6 and fix .pyproj
Switch to Python 3.6 and fix .pyproj

See the following commits on ThScoreFileConverter:
8d764c7adf38baeea629c4634b6fc2f70926a25f
2828a8470b1deb6b172a51c60a3e64586a25534c
5107986e55b7140f25b2742d37f61df233843f0f

y-iihoshi/REIMU_Plugins_V2,y-iihoshi/REIMU_Plugins_V2