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 if you are happy to push this change onto the Pull Request, we can get it pulled in.