Fix graph_wo_index to use mixable helper
Fix graph_wo_index to use mixable helper

rimms/jubatus_core,kmaehashi/jubatus_core,gintenlabo/jubatus_core,rimms/jubatus_core,kumagi/jubatus_core,kmaehashi/jubatus_core,kmaehashi/jubatus_core,kumagi/jubatus_core,kumagi/jubatus_core,kumagi/jubatus_core,gintenlabo/jubatus_core,gintenlabo/jubatus_core,rimms/jubatus_core,gintenlabo/jubatus_core,rimms/jubatus_core,kmaehashi/jubatus_core