Better pretty-printing

This PR introduces `(with-out-str (clojure.pprint/pprint ...))` as a method of pretty-printing instead of pr-str. There is also a little CSS change. Here is a comparison: [before](https://f.cloud.github.com/assets/316910/523346/07880888-c0ae-11e2-9a69-0c1bf420ea23.png) and [after](https://f.cloud.github.com/assets/316910/523344/f5550300-c0ad-11e2-8d46-04c3e71b1aab.png).