Confusing curl test results

[rhattersley]

The work on CF-style coordinate systems (#65) highlighted a possible issue with spherical curl.

As a result of #65, the unit of the radius changed from "km" to "m".

1. Should the results in the test_contrived_spherical_curl1 and test_contrived_sphrical_curl2 have been divided by 1000?
2. Are the values of the decimal keyword sufficiently strict?

[bblay]

Also related to this are the two test result files, here and here
whose units are 1000 times smaller.