Port to python 3

[cbalint13]

Proposed patch series ports all portions of the code to python 3.

• It includes:

  • code requires python 3 noew
  • build script have simple test case
  • it works with matplotlib > 2.x (also python3 only lib)
  • working examples can use optionally latest pySmithPlot (also python3 only lib)

All credit goes to @Psynosaur and his fork , he agreed to help commit the work here.