Add auto completion

[bmcculley]

For the ultra lazy like myself, it would be great to be able to autocomplete.

I don't have a windows box currently so I can't create a powershell demo but I created a bash demo, it can be found in this gist (setup instructions in readme).

The following would then be possible:

$ psa <tab> <tab>
bounce     flush      kill       purge      start      stop       
configure  help       list       restart    status 
$ psa r<tab>
$ psa restart <tab> <tab>
app   prcs  web

What are the thoughts on adding something like this?