Sprout 111 update onyx version

So looks like it's actually 2.7.3 now.  Sad how out of all the mirrors online to download this dmg, not one is direct link-able except the author's site, and that link doesn't have a static version.  Seems like he updates the version but uses the same url, so we'll always have the right link to latest but not version or checksum :-\

Fixes #111