Fix most markdownlint errors (#745)
Fix most markdownlint errors (#745)

Here I fixed all but the errors for rules MD013, MD001, MD012, MD033 as per
the proposed checks in #745.

I was able to filter these out with:

   $ markdownlint WorkingEffectivelyWithLegacyCode.md 2>&1 \
     | grep -v MD013 | grep -v MD001 | grep -v MD012 | grep -v MD033

and it comes back clean.

betterscientificsoftware/betterscientificsoftware.github.io