Add test for put_diff and get_diff
Add test for put_diff and get_diff

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