gitignore: Add example build folder and sublime project files

MegaDuck: safer bit ordering revesal & use more defines (thx toxa)

- Also fix typo in Readme

Readme: Tidy up a little

Remove `halt` in GBS init (SuperDisk#29)

Appears to fix compatibility with NEZPlug++, at least.
(And also `gbsdiff`, but that's a story for later.)