* [fix] Fixed intendation for flake8
* [feat] special module with Bessel functions added.
* [feat] init adapted.
* [tests] First test for special module added.
* [tests] Check kn special function derivative explicitly vs numerical
derivative of scipy function.
* [feat] Added remaining autograd scipy special functions to the special
module.
* [feat] Imports corrected, docstring added.
