This module subclasses numpy's array type, interpreting the
array as an array of quaternions, and accelerating the algebra
using numba.  This enables natural manipulations, like multiplying
quaternions as `a*b`, while also working with standard numpy
functions, as in `np.log(q)`.  There is also basic initial support
for symbolic manipulation of quaternions by creating quaternionic arrays
with sympy symbols as elements, though this is a work in progress
