Returns neighbors and updates neighbor bomb counts
Move neighbors and neighbor_bomb_count to Board.
Complete bomb reveal and loss; almost perfect board reveal
Fix reveal so that diagonal neighbors are not revealed.
Add error handling for move type selection.
Breaks classes into different files and allows players to flag/unflag tiles correctly
Can win by revealing all non-bombs or flagging all bombs
Fix render to display coord numbers and fix bomb render to not override flags when losing game
Delete old minesweeper.rb