Working on testing lecture for Python

Working on testing lecture for Python

W. Trevor King: This is a IPython Notebook translation of Greg's unit
testing content, which he initially developed in 2010 in Software
Carpentry's Subverison repository.  Unfortunately, the content of that
repository was in binary formats (ODF, PNG, etc.), so I can't graft it
on here in any useful way.  Interested parties should check out:

0a39643 Relocating test material, 2010-08-24
  4.0/site/test/unit.html → 4.0/topics/test/unit/test-unit.html

baccde4 Script for lecture on unit testing with Nose, 2010-08-18
  4.0/site/test/unit.html

b37a2f4 Blocking out unit testing lecture, 2010-08-04
  ...