New "Ode to Joy" example
New highpass.z strategy (and used as default)
New math dir with highpass.z proof, with Sympy
New math README;highpass.z design allow negative R
MANIFEST.in include tests, examples, maths, docs
Project files section in README.rst
Math proof for 4 filters lowpass_highpass_pole_z
New lowpass.z single pole single zero strategy