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 #c694ff visited link colour versus #135684 footer background colour results in a 3.37:1 contrast ratio which is below the 4.5:1 minimum required by WCAG 2.0.