Syntax highlighting and better font in CSS

Additions:

1. highlightjs with github theme for syntax highlighting 'pre code' blocks (linked from CDN)
2. link to web fonts from [brick.im](http://brick.im), better quality than google.com/fonts

 2.1 Use google's Noto Sans unicode font, looks great on all devices
 2.2. Adobe's Source Code Pro monospaced font for pre and code blocks

Fix: 
* html doctype and charset