Enhance update check

[glinton]

trafficstars

Print update notice at the end of the output stream. Notify on commands following an update check that they still haven't updated (rather than next time we check)

[danhunsaker]

I'd personally still notify during the initial check, so at the beginning of the output, but then remind at the end as well.

There've been a few times I saw the update notice as I started a deploy and was about to move on to something else.