added vagrant instructions to readme, rework common role

README.md

@@ -24,7 +24,8 @@ ansible -m setup hostname
 ### Installing and starting Vagrant on ArchLinux
 Inside the cloned ansible folder, run these commands
 
-```` pacaur -S vagrant-libvirt
+```` bash
+pacaur -S vagrant-libvirt
 CONFIGURE_ARGS='with-ldflags=-L/opt/vagrant/embedded/lib with-libvirt-include=/usr/include/libvirt with-libvirt-lib=/usr/lib' \
   GEM_HOME=~/.vagrant.d/gems GEM_PATH=$GEM_HOME:/opt/vagrant/embedded/gems PATH=/opt/vagrant/embedded/bin:$PATH \
   vagrant plugin install vagrant-libvirt