Add timeout option to tests

[jamesoff]

See #33. Add an option to make a test fail if it's taking too long.

[jamesoff]

Note self: https://pypi.python.org/pypi/subprocess32/

[jtrip]

Thanks for your work on this James. Is this where I might want to manually adjust the timeout for now if I am currently only concerned with http?

https://github.com/jamesoff/simplemonitor/blob/master/Monitors/network.py

    def run_test(self):
        # store the current default timeout (since it's global)
        original_timeout = socket.getdefaulttimeout()
        socket.setdefaulttimeout(5)

[jamesoff]

Yup, that's the one.

[jamesoff]

#56 may be of use here as it looks like job execution can be given a timeout.

[jamesoff]

Should be able to handle this now that monitor evaluation is multithreaded, but I don't see a straightforward way to specify different timeouts for different monitors with it. Bumping for 1.12 while I think about it.