Add new Getting Started page

Modified content in start-en.hbs to match the new theme, 
Added page specific css in content/_base,scss
Modified colours in main/_base.scss and footer/_base.scss
Modified link colours in _variables.scss 
The links should be in a block level element like a <code>p</code>. Also add a closing slash to the </code>img</code> element for XHTML compatibility (<code>&lt;img /&gt;</code>).