Does not work with CentOS 6.3

I tried using this with CentOS 6.3, and it failed when trying to install git.  In shell/main.sh, it has a hardcoded value of ```YUM=/usr/sbin/yum``` for the yum location.  ```yum``` is actually located in /usr/bin on this system.  Instead of hardcoding the value, it would be better to dynamically find it.  I'll make that change and issue a pull request.