Remove use of 'goto' in chisels to improve Lua 5.2 compat (issue #148)

Not claiming this is all that needs to be done (or that it isn't), but it's a start, and should fix the reporter's syntax error harmlessly.

If you're worried about compatibility with user-created chisels not in the repo, we could do something like:

    ansiterminal["goto"] = ansiterminal.moveto

however I'm not that much inclined to backwards-compatibility cruft, especially for such a young project :)