Tk add_two.py runs.

The tk sample of addign two numbers now runs.  Not that tk doesn’t run
in general, just this demo.   This is all proof of concept, and will
need a tossed out design onceI know more.
Documentation/replan updates...

Time to rethink everything again.
Start Travis CI tests

Run just simple unit tests on each commit.
Stub html_add_two.py

Start a demonstration program for html.