title: route for username to go to a profile#show
body: <p>I have a User model, where users have a username, and User has_one :profile</p>
  
  <p>I want to make a route so that if a person goes to "<a href="http://www.website.com/username" rel="nofollow">http://www.website.com/username</a>" it goes to profile#show.</p>
  
  <p>at the bottom of my routes, i have:</p>
  
  <pre><code>match ":username" =&gt; "profiles#show"
  </code></pre>
  
  <p>But, it's not finding the ID of the profile, which I expected.</p>
  
  <pre><code>ActiveRecord::RecordNotFound in ProfilesController#show
  Couldn't find Profile without an ID
  </code></pre>
  
  <p>I just am not sure how to properly make the route so i get the id of the user from the :username</p>
  
  <p>thanks</p>