split the latter half of highlight.pack.js into a separate file which
registers all the languages and exports hljs. this is for nodejs
compatibility and mimics the way the highlightjs module works in nodejs.
The current implementation of the highlight plugin only works properly
in the browser, and doesn’t work under Node.js. It also doesn’t work
when rendering to the fakedom in the browser (as happens when rendering
stylesheets, for example).
