Return false for timed-out `isOnline` calls

There's an ask involved in resolving isOnline, which, though it seems
unlikely, could possibly time out. If this happens, we don't want that
AskTimeout exception to escape and blow things up. So, call a timeout
"false", and let the polling take care of the rest.
Add better timeout test
Merge pull request #87 from clinedome-work/isonline-timeouts

Return false for timed-out `isOnline` calls