- updated table to 2 bytes (int16) per element and scaled the inclination/declination/strength tables to use most of the range without being too awkward
- tables have been extended to include the full latitude range
- expanded the API slightly to offer declination/inclination in both degrees/radians and the magnetic strength in Gauss and Tesla
- generated some simple testing that verifies interpolation between points
* Unfortunately, due to the SWIG dependency, we need sudo to install on
Travis (conflicts when adding with debian-sid source prevent using addons)
which means we cannot use the container-based infrastructure anymore.
* Building the Python bindings requires g++5 (at least with -Werr set).
* When building the Python bindings on Travis, the numpy includes are not found
by cmake, so they have to be added separately by running a Python process with
`numpy.get_include()`
* The build script now (somewhat clumsily) depends on the RUN_PYTEST environment
variable. If it is set to anything other than "", it will make the tests and
run tests and benchmarks