Radial basis function interpolation

With radial basis function interpolation, numericalnim finally gets an interpolation method which works on scattered data in arbitrary dimensions!

Basic usage:

let interp = newRbf(points, values)
let result = interp.eval(evalPoints)

What's Changed

• Radial Basis functions by @HugoGranstrom in #33

Full Changelog: v0.8.3...v0.8.4