TODO: Add more prom programming formats.

[dj-on-github]

The code currently support the intelhex format, which is possibly the least nice format of the usual suspects.

Let's add some more output formats.
Straight Ascii Hex
Straight Binary
Motorola S records

Also it would be nice to add support to write to a file. E.G.
asm6502.prom_output(self, format="intelhex", filename=None)
Set filename to have it write to a file and set format to one of "intelhex", "srecords","binary" or "hex".