Removes h1 in button

<h1> is not allowed in <button> in this context.
Edits logo area styles

Moves logo text into an <h1> and comments out currently unused CSS.
Adds CSS that moves about screen out of view

On Opera and IE pointer events are not supported, therefore the about
screen needs to be moved out of view after it is shown.
Fixes integration test for about screen
Merge pull request #72 from codeforamerica/html-validation

Html validation