Revert "Fix passing of producer args from SQL::Translator::Diff."

[rabbiveesh]

Reverts #117

broke the tests for SQLT-Diff, producer_args really is args for SQLT directly

[rabbiveesh]

@racke sorry, had to revert your PR.

For now, to accomplish your use case, you need to pass producer_args as a key to producer_args.

I'm going to make a different key that changes the API to use sqlt_args instead of producer_args so that this is more obvious, and it'll warn on the old usage.