Generalise regular interpolation.
Extended the env variables for Iris's travis-ci testing.
Review changes.
Fix cube.copy() for scalar cubes.
Merge pull request #1381 from rhattersley/generalise-interp

Generalise regular interpolation.
Ran the system tests with default tests on travis.ci.
Fix vector dims shape for scalar value
Merge pull request #1409 from pelson/doctest_separate

Extended the env variables for Iris's travis-ci testing.
Merge pull request #1412 from dkillick/fix_no_dims

Fix vector dims shape for scalar dims
Merge pull request #1411 from pp-mo/scalar_cube_copy

Fix cube.copy() for scalar cubes.
Import pygrid via iris.proxy for full optionality.
Skip pyugrid tests if it's unavailable.