BUG: Fix redirect link to work on IE
BUG: Fix redirect link to work on IE

IE doesn't correctly understand the url. Affixing the base reference stops it from getting confused.
silverstripe-labs/silverstripe-newsletter,guru-digital/silverstripe-newsletter,silverstripe-labs/silverstripe-newsletter,silverstripe-labs/silverstripe-newsletter,guru-digital/silverstripe-newsletter,guru-digital/silverstripe-newsletter,silverstripe-archive/silverstripe-newsletter,silverstripe-archive/silverstripe-newsletter