Load jQuery with a relative protocol URL

In Chrome 36.0.1985.125 on OSX 10.9.4 I get this error:

[blocked] The page at 'https://benpickles.github.io/peity/' was loaded over HTTPS, but ran insecure content from 'http://ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js': this content should also be loaded over HTTPS.

This is fixed by making the URL protocol-relative.