add type() interface to dummy_mixer (refs #754)
add type() interface to dummy_mixer (refs #754)

rimms/jubatus,kmaehashi/jubatus,jubatus/jubatus,mathn/jubatus,Asuka52/jubatus,roselleebarle04/jubatus,rimms/jubatus,mathn/jubatus,gintenlabo/jubatus,elkingtonmcb/jubatus,Asuka52/jubatus,elkingtonmcb/jubatus,jubatus/jubatus,jubatus/jubatus,kmaehashi/jubatus,roselleebarle04/jubatus,gintenlabo/jubatus