Changeable keybindings

[matthewbauer]

Right now the keybindings are defined in src/renderer/player.coffee as

keymaps =
  'player':
    'y': 'joypad:0:y'
    'x': 'joypad:0:x'
    'b': 'joypad:0:b'
    'l': 'joypad:0:l'
    'r': 'joypad:0:r'
    'ArrowUp': 'joypad:0:up'
    'ArrowDown': 'joypad:0:down'
    'ArrowLeft': 'joypad:0:left'
    'ArrowRight': 'joypad:0:right'
    'Enter': 'joypad:0:start'
    'Shift': 'joypad:0:select'
    'k': 'joypad:0:b'
    'j': 'joypad:0:y'
    'l': 'joypad:0:a'
    'i': 'joypad:0:x'
    'a': 'joypad:0:left'
    's': 'joypad:0:down'
    'd': 'joypad:0:right'
    'w': 'joypad:0:up'

These should be configurable by the user.