title: Hiding a button after a purchase with MKStoreKit
body: <p>Been wrangling with MKStoreKit 3.0 for the first time... and nearly everything is good for me; things purchase, userdefaults are set, I've got UIbuttons that hide after reboots.  But I seem to have tripped at a very elementary step.</p>
  
  <p>How do I make my 'buy' UIbutton hide after purchases and re-purchases?  Is there a function hidden in MKStoreManager.h that I'm yet to discover? Or should I just get the buyfeature action to twiddle its fingers for a while then check to see if a purchase has happened in the intrim?</p>