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 
I will be changing the footer's colours again to reach a better contrast ratio. I am giving the footer a gray background and dark blue text, which should solve this issue. The gray background should be matching the menu bar to create a visual balance. This means the menu bar should eventually have the same gray background. This will also result a separation from the header and the menu. Currently they are blending together which could be a usability issue.