remove deprecated module, rpmkit.shell2
add rpmkit.utils.pcall, an wrapper function of multiprocessing.Pool.map, etc. and its test cases
remove dependency to gevent and make use of rpmkit.utils.pcall instead
add an utility function to swap multiprocess.Process to call cmd in given workdir into rpmkit.utils
remove dependency to gevent and make use of rpmkit.utils.run_cmd_async instead
add the latest changelog entry in %changelog section in the RPM spec