radbelt: Astropy-friendly wrapper for the AE-8/AP-8 Van Allen belt model(GSC-18816-1)

This is small Python library to model the fluxes of charged particles trapped in the Van Allen belt. It provides a fast, simple, and convenient Python interface to the International Geomagnetic Reference Field (IGRF) model and NASA's AE-8/AP-8 models of electron and proton fluxes, which are both implemented in Fortran.