Frontend: Syntax highlighting for Python 3

[olehermanse]

Syntax highlighting and decent formatting would improve the service a lot. I consider python 3 and javascript to be the most important languages to support. A drop-down to switch between them seems appropriate.

[olehermanse]

@michaelpande This looks promising? https://github.com/isagalaev/highlight.js
Or: http://prismjs.com/