Fix implementation of byte_buffer::assign
Fix implementation of byte_buffer::assign

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