enhance build. add single point and test

allow CMake >= 3.10
bugfix: don't rebuild each import

enhance build, add features

• enhance build-on-run using latest Python 3.7 and CMake techniques
• add CMake self-test
• added transect function that computes and returns arbitrary paths through the wmm (@anielsen001)
• added error checking for input of two 1-D arrays (@anielsen001)

initial release

v1.0.0

update test data