Update README.md

Fix & update instructions for CentOS

* Replace `libboost-devel` with `boost-devel` — http://serverfault.com/questions/445904/how-to-install-libboost-devel-on-centos-6-3
* Also install `g++`
* Adjust `tar` options order — http://superuser.com/questions/211941/why-cant-z-be-the-last-command-line-option-to-be-used-with-tar
Merge pull request #12 from jibiel/patch-1

Update README.md