ObsPy test doesn't work any more

The ObsPy test stopped working on about 10/31/2017 with the following error:

 pkg_resources.DistributionNotFound: The 'pytz' distribution was not found and is required by matplotlib

I couldn't figure out how to fix it on short notice, so I disabled it for now.

As an aside, this also reduced the Travis run time from 16–20 minutes to 5–6 minutes. I'm not sure this is a good use of test wall time. Perhaps the test can be shortened before returning it to service.