remove a broken, unfinished disassembler (DisAsm)

This removes DisAsm from romstr.py, which was the only reason that
gbz80disasm wasn't able to import RomStr from romstr.py.

DisAsm was an experimental gbz80 disassembler that was meant to replace
gbz80disasm eventually. The goals were to write cleaner code and write
more unit tests. But it never worked and the code quality looks close to
being the same as gbz80disasm anyway.

extras/gbz80disasm.py

@@ -9,15 +9,13 @@ import random
 
 spacing = "\t"
 
-class XRomStr(str):
-    def __repr__(self):
-        return "RomStr(too long)"
+from romstr import RomStr
 
 def load_rom(filename="../baserom.gbc"):
     """loads bytes into memory"""
     global rom
     file_handler = open(filename, "rb") 
-    rom = XRomStr(file_handler.read())
+    rom = RomStr(file_handler.read())
     file_handler.close()
     return rom