Fix wrap try/catch C++ callback for libevent callback
Fix wrap try/catch C++ callback for libevent callback

fixes #48

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