Literate Programming: PyLit3

I've revised PyLit to work with Python3.

See https://github.com/slott56/PyLit-3

The code seems to pass all the unit tests.

The changes include Python3 revisions, plus a small change to handle trailing spaces in a sightly cleaner fashion. This was necessary because I have most of my editors set to remove trailing spaces from the files I create, and PyLit tended to create trailing spaces. This made the expected output from the unit tests not precisely match the actual output.