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 
"Start by choosing a flexible theme. Then find the components that meet your content needs. Finally, customize display elements such as buttons and icons." seems odd right after the sentence about variants. It reads like these steps are how to discover what variants are available.