Upgrade nunjucks
Upgrade nunjucks

There were some annoying bugs in the version we were using, including
broken behaviour for the `if` block in templates. Upgrading to the
latest version fixes some of those issues.

mozilla/openbadger,bdgio/msol-site,bdgio/msol-site,kayaelle/msol-badger,mozilla/openbadger,kayaelle/msol-badger,bdgio/msol-site,kayaelle/msol-badger