title: slack api rtm.start missing_scope needed client
body: <p>I have get access token and when I try to post rtm.start, I am getting below error:</p>
  
  <pre><code>{
      error = "missing_scope";
      needed = client;
      ok = 0;
      provided = "identify,read,post";
  }
  </code></pre>
  
  <p>I have set the scope to <code>read,post,identify</code> in authorize API. I have read the API document over and over again. Only <code>rtm.start</code> mentioned client scope. But in oauth document I didn't find a client scope. So, what's wrong? </p>