First user should sign up instead of being the root user

See https://gitlab.com/gitlab-org/gitlab-ce/issues/1980#note_4382951

Background:

Hello, I installed Gitlab 8.6.0 and once it started I was redirected to a "Change your password" page with the following message: "Please create a password for your new account.".

1. Which account?
2. Why should I change a password for an account I didn't even setup?
3. How am I supposed to know it's 'root' and I'm currently updating it's password?

The idea here is that the first introduction to Gitlab should be smoother with, for example, a welcome message and a wizard in which we can setup the username and password with confirmation.