title: Additional alert shows up using AppAuth to authenticate in swift4
body: <p>I am using <code>AppAuth</code> 0.90.0 for authentication using an external authentication server where a user can log in so the app receives appropriate authentication tokens. Since recently (after upgrade to swift 4) I get the following alert before I get sent to the authentication server:</p>
  <blockquote>
  <p>&quot;App Name&quot; Wants to Use &quot;externalAuthentication.com&quot; to Sign in&quot;</p>
  <p>This allows the app and website to share information about you.</p>
  </blockquote>
  <p>Has someone experienced the same issue and/or has a solution so the user does not need to press continue each time a request to that server is made?</p>