code: github.com/a1k0n/jsxm
todo:
 - file picker, upload more xms to a host we can access cross-origin
 - render instrument list in ft2 font
 - missing XM effects:
   - E3x, E4x, E5x, E6x, E7x, E9x, EDx, EEx
   - 7xy - tremolo
   - Gxx, Hxy, Kxx, Lxx, Pxy, Txy