0.8.4

Fixed

• Tree store: opening a store while another handle commits a group no longer reports "tree store
  is corrupt: a group whose event is missing". The open lists each tenant's group files before it
  reads the events, and reads only the listed groups; a group committed after the list is not read
  and its events are torn, as an interrupted write's are. A listed group whose event is missing
  is still refused.