reworked tabs to display as modals. 

Added padding to tarrif display to make it more visible on background.  (i.e. a little white box background appears)

Tabs now display as modals, so we're back to a single html page.  This prevents issues with the zip being-rerequested anytime the user returns to the homepage from a tab. (Not sure how to do it otherwise, as it's all stateless, e.g. couldn't pass around some "zipEnetered = true" variable to toggle zip request.)