Bug 855734 - Strip trailing "." from request host

People (several per day) are getting to mozilla.org via URLs like
http://www.mozilla.org./en-US/grants/. This causes the HTTP_HOST
header to be 'www.mozilla.org.', which doesn't match Django's
ALLOWED_HOSTS, which then throws errors. Apache redirect people
coming to the site with a HOST that ends in a ".".