title: Omniauth - set custom param in redirect url
body: <p>I'm using latest (1.0.1) version of Omniauth with rails 3.1.3.
  Right now, I'm using omniauth with 37signals strategy. I would like to pass custom argument ("state" parameter) depending on  auth url (eg. <a href="http://localhost:3000/auth/37signals/" rel="nofollow">http://localhost:3000/auth/37signals/</a><strong>5</strong> should redirect to <a href="https://launchpad.37signals.com/authorization/new" rel="nofollow">https://launchpad.37signals.com/authorization/new</a>?(...)<strong>&amp;state=5</strong></p>
  
  <p>I've tried to set (temporarily) fixed state, with something like</p>
  
  <pre><code>provider "37signals", "my_client_id", "my_secret", {state: "5"}
  </code></pre>
  
  <p>However, in my url there is (still) no state param.
  Any ideas why? Is it possible to set that param?</p>