Add travis.yml

[trexfeathers]

Base on those included in other SciTools repos (tephi as usual being the flagship example).

• Will need to custom install iris (this commit) and iris-test-data (this commit).
  See how iris' Travis does iris-test-data for details.
• Travis should reference a requirements txt file - see Add requirements text file(s) #6.

Enforce the following coding standard:

• Use pytest
• Use pytest-xdist
• Use coverage
• Maintain flake8 compliance
• Maintain black compliance
• Configure pre-commit git hooks, as per iris

[trexfeathers]

See #14 for black and pre-commit

[trexfeathers]

This repo has been superseded - loading UGRID is now incorporated into SciTools/iris, and the regridding has migrated to SciTools-incubator/iris-esmf-regrid.