Add Debug instance for MatchOptions

[ndmitchell]

It's pretty useful when debugging to have a Debug instance available. I have a record in my project, for which I'd like Debug, but it's slightly complicated because it embeds a MatchOptions in it. Would it be possible to derive Debug for MatchOptions?

[JohnTitor]

That has been added by #91, we have to cut a new release including it.

[JohnTitor]

0.3.1 is now released, closing as done.