Fixed invalid HTML

- Moved footer within the body
- Added alt attribute to images
- Changed doctype from XHTML1 to HTML5
Social meta tags

- Added social meta tags so the image is always the same (a real
designer should come with something better)
- included the image
Moved css and js to separate files

- Moved the CSS from the index to mappit.css
- Moved the JS from the index to mappit.js