Add back latest version of CodeMirror.
Move init.js to js/init.js.
Add a new makeCodeMirror editing function.

This is going to be used for all syntax highlighting throughout the
presentation, instead of the highlighting plugin that comes with
reveal.js, since those two highlighters were not playing well together.
Disable and remove the reveal.js highlight plugin.
Regenerate node_modules/transforms/bundle.js.
Convert <pre> tags from highlight plugin style to CodeMirror style.
Mirror/highlight all <pre data-language> nodes.
Fluent/Pivotal tweaks.
Spacing tweaks.