message: pull down msgpack sources from github
diff: #!/usr/bin/env bash
  +##
  +## if you are behind a firewall, set a proxy
  +##
  +## export http_proxy=http://your_ip_proxy:port/
  +## export https_proxy=$http_proxy
  +##
  +
  +# get msgpack-c
  +version=2.1.1
  +tarfile=cpp-${version}.tar.gz
  +echo '***' fetching msgpack-c $version '***'
  +echo
  +
  +test -f $tarfile || wget https://github.com/msgpack/msgpack-c/archive/$tarfile
  +
  +if [ -f ${tarfile} ]; then
  + tar xfz ${tarfile} -C external --transform "s/msgpack-c-cpp-${version}/msgpack-c-cpp/"
  +else
  + echo failed to download ${tarfile} ... please try manually
  +fi
  +unset version tarfile
  -# if you are behind a firewall, set a proxy
  -#export http_proxy=http://your_ip_proxy:port/
  -#export https_proxy=$http_proxy
  # get googletest
  googletest_ver=1.8.0
  