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 
This seems to be an odd link since it links to the very next line of text on the page. It would probably make more sense to make "I want to make a pull request" a sub-section of this section.