math

cc8e300b - Update I0 and I1 to use better approximations from Pavel Holoborodko

Update I0 and I1 to use better approximations from Pavel Holoborodko See: http://www.advanpix.com/2015/11/11/rational-approximations-for-the-modified-bessel-function-of-the-first-kind-i0-computations-double-precision/