for now:
- rom2cart doesn't fully support type 57, standard 2K cart, because it
  assumes all cart images are a multiple of 4K in size.

later:
- add cassio?
- file magic? (finish it, see if file upstream wants it)
- new tool: a8grep. knows about xex files (but works on others), can
  search for screen codes or inverse video, etc. also a8strings.
- new tool: something like ataricom or binload, but show checksums
  of segments (so we can compare different versions of the same game).