Update README to note libvirt-dev requirement

The libxml-devel note was helpful, but I needed libvirt-devel too
Merge pull request #12 from supercow/libvirt-dev_doc_update

Update README to note libvirt-dev requirement
Tool for RedHat image preparation.
Fix for requiretty disabling in sudoers file.
Don't use DNS in /etc/ssh/sshd_config file setup.
Switch off iptables and SELinux to permissive mode.
IP of VM is searched in dnsmasq lease files only.
Provider options cpu and memory added. Those are used while creating
a new domain.
v0.0.3
Version changed to 0.0.3
fix run_provisioner