swc-installation-test-2.py: Comment out unused checks

We don't need this stuff for 2014-03-uwash's Python room.
Replace '&times;' with U+22C5 DOT OPERATOR

This makes the source easier to read in a UTF-8-capable editor.
Replacements made with:

  sed -i 's/&times;/⋅/g' shell/*.md python/*.ipynb
shell/00-intro.md: Use reference-style links

This makes reading the source easier, because the long URLs aren't
breaking up your sentences.  It also isolates textual changes from URL
changes in diffs.