Add CentOS git install support.

Although this adds CentOS git install support, there's something wrong with both git and stable installations, there's no "next" step once installed.

For stable:
```
Installed:
  salt-minion.noarch 0:0.10.3-1.el6                                             

Dependency Installed:
  PyYAML.i686 0:3.10-3.el6                                                      
  libyaml.i686 0:0.1.3-1.el6                                                    
  m2crypto.i686 0:0.20.2-9.el6                                                  
  python-babel.noarch 0:0.9.4-5.1.el6                                           
  python-crypto.i686 0:2.0.1-22.el6                                             
  python-jinja2.i686 0:2.2.1-1.el6                                              
  python-msgpack.i686 0:0.1.9-2.el6                                             
  python-zmq.i686 0:2.2.0-4.el6                                                 
  salt.noarch 0:0.10.3-1.el6                                                    
  zeromq3.i686 0:3.2.0-0.3.20121009git1ef63bc.el6
[default] Complete!
[default]  * Running install_centos_63_stable_post()
[default]  * Salt installed!
[default] [WARNING ] Setting up the Salt Minion "localhost.localdomain"
[default] [ERROR   ] This master address: 'salt' was previously resolvable but now fails to resolve! The previously resolved ip addr will continue to be used
[default] [ERROR   ] This master address: 'salt' was previously resolvable but now fails to resolve! The previously resolved ip addr will continue to be used
[default] [ERROR   ] This master address: 'salt' was previously resolvable but now fails to resolve! The previously resolved ip addr will continue to be used
[default] [ERROR   Installed:
  salt-minion.noarch 0:0.10.3-1.el6                                             

Dependency Installed:
  PyYAML.i686 0:3.10-3.el6                                                      
  libyaml.i686 0:0.1.3-1.el6                                                    
  m2crypto.i686 0:0.20.2-9.el6                                                  
  python-babel.noarch 0:0.9.4-5.1.el6                                           
  python-crypto.i686 0:2.0.1-22.el6                                             
  python-jinja2.i686 0:2.2.1-1.el6                                              
  python-msgpack.i686 0:0.1.9-2.el6                                             
  python-zmq.i686 0:2.2.0-4.el6                                                 
  salt.noarch 0:0.10.3-1.el6                                                    
  zeromq3.i686 0:3.2.0-0.3.20121009git1ef63bc.el6
[default] Complete!
[default]  * Running install_centos_63_stable_post()
[default]  * Salt installed!
[default] [WARNING ] Setting up the Salt Minion "localhost.localdomain"
[default] [ERROR   ] This master address: 'salt' was previously resolvable but now fails to resolve! The previously resolved ip addr will continue to be used
[default] [ERROR   ] This master address: 'salt' was previously resolvable but now fails to resolve! The previously resolved ip addr will continue to be used
[default] [ERROR   ] This master address: 'salt' was previously resolvable but now fails to resolve! The previously resolved ip addr will continue to be used
```

For git:
```
[default] changing mode of /usr/bin/salt-call to 755
[default] running install_data
[default] copying doc/man/salt-master.1 -> /usr/share/man/man1
[default] copying doc/man/salt-key.1 -> /usr/share/man/man1
[default] copying doc/man/salt.1 -> /usr/share/man/man1
[default] copying doc/man/salt-cp.1 -> /usr/share/man/man1
[default] copying doc/man/salt-call.1 -> /usr/share/man/man1
[default] copying doc/man/salt-syndic.1 -> /usr/share/man/man1
[default] copying doc/man/salt-run.1 -> /usr/share/man/man1
[default] copying doc/man/salt-minion.1 -> /usr/share/man/man1
[default] copying doc/man/salt.7 -> /usr/share/man/man7
[default] running install_egg_info
[default] Writing /usr/lib/python2.6/site-packages/salt-0.10.3-py2.6.egg-info
[default]  * Running install_centos_63_git_post()
[default] Starting salt-minion daemon:
[default]  * Salt installed!
[default] [  OK  ]
```

They both reach the `* Salt installed!` point, so, the whole script was executed. Dunno what's happening. I'll update my CentOS vagrant image once I get home and retry.