nobs should handle internet problems nicely

[john bachan]

The internet is faulty, and by default we use the internet to download gasnet. Sometimes this times out or has a certificate failure. Nobs should catch both and print nice messages before death.

[john bachan]

Fixes issue 119.

Nobs now gracefully chokes on connectivity issues when attempting to download gasnet. Timeouts, server down, and bad SSL have all been verified as graceful.

→ <<cset 67a8f09b8d8d>>

[john bachan]

Fixed by commit 67a8f09

[Dan Bonachea]

verified - thanks John!