Added psync(port sync), updated puni, puo

Added psync(port sync) to performs a sync operation only on the ports tree of a MacPorts installation, pulling in the latest revision available of the Portfiles from the MacPorts rsync server.
Added -u option to puni,puo so that it uninstall non-active ports when upgrading and uninstalling.
```
[~ZSH/plugins]$ sudo port sync                                                                                                              [master][ruby-2.1.1]
--->  Updating the ports tree
[~ZSH/plugins]$
```