Query of Notary needs a timeout

[von]

Copy of von/PerProxy#7

Current it will just hang if Notary does not respond.

Querying Notary at cmu.ron.lcs.mit.edu port 8080 about encrypted.google.com:443,2...

What's a reasonable default timeout? 1 second?

[von]

The issue here was that asyncore.loop() has no functionality to do a total timeout on the loop. The 'timeout' parameter is only for each individual call to select() and the 'count' parameter does put a bound on the number of calls to select, but that's not deterministic. So I created timed_asyncore.loop_with_timeout() which treats 'timeout' as a total maximum time the loop should run.