Update README.md to add link to Customize section of pure-site

The Customize section of the website will be updated with a link to cdnjs.

Closes #123
Update HISTORY.md for 0.2.1 to add module section headings
Add missing issue numbers to 0.2.1 HISTORY, tag people, and make links
Organize and tweak v0.2.1 HISTORY entires
Fix typo in HISTORY.md
Merge pull request #138 from ericf/history-0.2.1

Update HISTORY.md entries for v0.2.1, Closes #136