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 
@burgvan The normal convention is to link to the theme index page (for working examples) which includes a link to the documentation. Regardless of where the link points, the link text should be clearer as to what is the actual target. If you are targeting the documentation then include that in the link text. If you are targeting the examples then include that in the link text instead. Either way, we should not be leaving the link text so ambiguous.