Add Timeout to Crawlers

[davewichers]

If a test case never responds, the crawler stops and waits forever. Add a response timeout to BenchmarkCrawler so it will drop the request, and continue properly.

[JonathonWichers]

The timeout has to be longer than I though. Like 5 minutes, as it significantly depends on the speed of the machine. In fact, by default, the timeout should be disabled, and should be set via a command line param, rather than be fixed.