chore(purchase.html): Readd former purchase page

Apparently we need the link to Wufoo to stay for a while longer
until the move over to FoxyCart is completed.
chore(foxy_purchase.html): Rewording, add license agreement.
chore(foxy_purchase_discount.html): Add page for discount purchases

This page will allow purchasing for those who have the 30% discount
enabled.