New Homepage

This PR documents the creation of new homepage according to the mock shared via email.
Also tweaked the styling for sign up page.
Hmm, that's a great point Nikil.  I think there is value in giving people an easy way to change their minds.  The alternative, I guess, would be to have users hit the 'back' button, or click on the logo to go back.  This latter option makes sense to me, but I wonder what Tony thinks.

Not sure how most websites do this, I couldn't find many examples, but the signup page for https://www.heroku.com/ just uses the logo as a link.