Update cyg-get

Update cyg-get to be able to run straight after installing cyg-get, if you don't close and reopen Powershell after installing cyg-get (spawning a new Powershell within doesn't work), cyg-get doesn't work. This will make cyg-get find the cygwinsetup.exe without restarting Powershell.
@RyanCarrier I am more concerned about the path the user is sitting on at the completion of the command. If it switches the path to somewhere else without putting it back at the completion, that could be a little surprising and irritating for users.