Add .nojekyll to public

There's a rake task (`copydot`) that moves over dotfiles for us; let's
use it. It's already integrated in the deploy.

Change-Id: I7f801c88997a58f7a19aed3a8b2e1aac6c6d94fa
Reviewed-on: https://gerrit.causes.com/23037
Reviewed-by: Aiden Scandella <aiden@causes.com>
Tested-by: jenkins <jenkins@causes.com>