title: Access tokens expire after only 1 day
body: <p>With my Flattr client using the REST API, it seems that access tokens expire after 1 day. I checked my settings and the client is still authenticated. But when I issue a request to <code>https://api.flattr.com/rest/v2/user</code> I get the following response:</p>
  
  <pre><code>{ 
     "error":"unauthorized",
     "error_description":"You are unauthorized to access the resource",
     "error_uri":"http:\/\/developers.flattr.net\/api"
  }
  </code></pre>