Restructure valid moves collection to flat scheme

Switch valid moves collection from a hierarchical style to a flat
non-normalized style in preparation for the adding of the special En
Passant and Castling moves
Add en passant capturing, github issue #3
Add castling, github issue #1
Add basic pawn promotion, github issue #2

Currently a pawn become a queen. Need to add a popup window to let the
user select from a rook, knight, bishop, or queen
Fix "refresh page sets active player to black" bug

Before this when a page was refreshed it would alway set the active
player to white. Valid moves collection was not affected.
Update version to 0.1.0