include embedded repl

[shaunlebron]

himera was updated to latest cljs, so maybe we can embed this in the website somehow:

• live: http://geit.fikesfarm.com/
• code: https://github.com/mfikes/himera

a bigger idea would be to have the docs pages have editable examples using this.

[shaunlebron]

the new cljs.js namespace in the next release will include the bootstrapped compiler, so we can have a fully client-side repl.