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
  ...

Many files meant to be used as includes had somehow been transformed
into standalone HTML files.

The extra header and footer boilerplate has been removed, and
single-quoted attributes have been turned into proper double-quoted
attributes.

W. Trevor King: I dropped everything from the original 6a4f3fb except
for the LICENSE.md and lessons/swc-python/ears.py additions.  I also
added a blank line to Greg's commit message for cleaner 'git log
--oneline' formatting.

Conflicts:
_includes/banner.html
_includes/bootcamps/contact.html
_includes/bootcamps/eventbrite.html
_includes/bootcamps/instructors.html
_includes/bootcamps/python.html
_includes/bootcamps/r.html
_includes/bootcamps/requirements.html
_includes/bootcamps/what.html
_includes/bootcamps/who.html
_includes/footer.html
_includes/guide-db/aggregate/challenges.html
_includes/guide-db/aggregate/challenges/average-null.html
_includes/guide-db/aggregate/challenges/concat.html
_includes/guide-db/aggregate/challenges/count-ave-temp.html
_includes/guide-db/aggregate/challenges/diff-with-average.html
_includes/guide-db/aggregate/keypoints.html
_includes/guide-db/aggregate/lesson.html
_includes/guide-db/calc/challenges.html
_includes/guide-db/calc/challenges/adjust-salinity.html
_includes/guide-db/calc/challenges/missing-units.html
_includes/guide-db/calc/challenges/union.html
_includes/guide-db/calc/challenges/unique-major-site-ids.html
_includes/guide-db/calc/keypoints.html
_includes/guide-db/calc/lesson.html
_includes/guide-db/create/challenges.html
_includes/guide-db/create/challenges/dump-version-control.html
_includes/guide-db/create/challenges/insert-olmstead.html
_includes/guide-db/create/challenges/replace-null.html
_includes/guide-db/create/keypoints.html
_includes/guide-db/create/lesson.html
_includes/guide-db/distinct/challenges.html
_includes/guide-db/distinct/challenges/distinct-dates.html
_includes/guide-db/distinct/challenges/distinct-vs-sort-uniq.html
_includes/guide-db/distinct/keypoints.html
_includes/guide-db/distinct/lesson.html
_includes/guide-db/filter/challenges.html
_includes/guide-db/filter/challenges/fix-selection.html
_includes/guide-db/filter/challenges/out-of-range.html
_includes/guide-db/filter/challenges/select-like.html
_includes/guide-db/filter/keypoints.html
_includes/guide-db/filter/lesson.html
_includes/guide-db/grouping/challenges/date-range.html
_includes/guide-db/grouping/challenges/simplify-query.html
_includes/guide-db/grouping/challenges/trace-pipeline.html