Ruby mogilefs-client 3.2.0-rc1

* "list_keys" and "exist?" client commands raise errors properly
  on failure.

* backend connections no longer terminate on ERR responses, only
  on socket/connection errors.

* support the "updateclass" client command.  This is for updating
  the class of a given key and not to be confused with the
  "update_class" admin command.

* "new_file" checksum usage is now documented since MogileFS 2.60
  includes official support for checksums