Auto trigger CI

[justinlaughlin]

We want to have pymfem trigger its CI tests when mfem updates... The machinery is mostly in-place already, we just needed to decide on and enable the trigger.

I think we decided to use pushes to mfem:master as the trigger for CI on the pymfem side...

[sshiraiwa]

Great idea. Running minimum set of build and example test would be very helpful to detect an issue

building

1. python setup.py installl --mfem-branch=master
2. python setup.py install --with-parallel --mfem-branch=master

testting

1. cd test; python run_examples.py -serial -verbose
2. cd test: python run_examples.py -parallel -np 4

[justinlaughlin]

@sshiraiwa When you get a chance could you check out https://github.com/mfem/mfem/pull/4283 :)

The trigger runs {"test_options":"fast"} which builds and runs tests for --mfem-branch=[master,default] and parallel/serial. If we need to make changes, we should be able to just edit the code block on the PyMFEM end.