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 
Ideally these changes would be split across each of the relevant SCSS files rather than creating a new SCSS file. In each of those SCSS files be sure to continue nesting under .newdesign. When it comes time to make it global, we'll just integrate those .newdesign changes into those files properly.