Add web REPL UI based on Himera.

- Import base HTML, stylesheets and images from Himera
  (https://github.com/fogus/himera). Also, import synonym.html
  sibling file that has JavaScript to ClojureScript translations.
- Add src/cljs/webrepl2.cljs that implements the new REPL.

The new REPL can be built like this:

    cd web
    ../bin/cljsc ../src/cljs/webrepl2.cljs > webrepl2.js

Then open web/repl.html. The new REPL page has a much better design
and style with the reference/links from the Himera front page. The
REPL window is based on jquery.console and has history (up arrow)
support.