title: Sign in count per day in Devise
body: <p>Is there any way to find out how many unique logins per day a user has?</p>
  
  <p>We can track a user to find out how many sign_in's or when the user signed in with:</p>
  
  <pre><code>User.last.sign_in_count
  </code></pre>
  
  <p>or</p>
  
  <pre><code>User.last.last_sign_in_at
  </code></pre>
  
  <p>But not how many time he logged in each day.</p>