Added styles for modal

Ported over from my demo app, tried to match coding style
Added script for modals

*  Follows existing conventions throughout
Added a test page for the modal component
Added modal.(css|js) to build
Rebuilt ratchet
Documented modals

First run - we could probably extend this
* Used some custom CSS to make the position: fixed demo absolute.
Remove spaces around arguments
Styles on their own lines
Remove comment
Correct whitespace
Whitespace
Not required
Always return the result of querySelector
Test for truth
Use translate3d as well
Rebuild ratchet
Drop newline
Minimising getModal further

Thanks @fat!
Only use translate3d
Rebuild ratchet