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 It's before it reaches Travis so most likely your editor is configured to output spaces instead of tabs. Please make sure to configure your editor to output tabs when indenting and then change the indents with spaces to indents with tabs.