New post "Using scalaz.Unapply".

I think this pretty much covers it, yeah?

@ekmett @retronym @paulp @milessabin @larsrh, if you'd care to be credited with a different link (I've used a github/twitter mix here), please let me know.  Apologies @paulp if you aren't "Paul" in scalaz/scalaz@de31bfafce91931ea33f51c5a44407311df0260c.