title: Rails Devise add role based on signup path
body: <p>I'm building a <code>Rails 3</code> app, where I need to give users specific roles based on the path they take to sign up on the site. I am using Devise and Cancan.</p>
  <p>So for instance, the path</p>
  <p><code>new-fundraiser</code> (or <code>/users/new/fundraiser</code>)</p>
  <p>Needs to set <code>user.fundraiser = true</code> on user creation, and</p>
  <p><code>new-charity-user</code> (or <code>/users/new/charity</code>)</p>
  <p>Needs to set <code>user.charity_owner = true</code> on user creation.</p>
  <p>What is the easiest / best-practice way to accomplish this using Devise and Cancan?</p>