add requirements for building RPM package in README
add requirements for building RPM package in README

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