title: Error searching for messages with utf8 subject
body: <p>I'm trying to read messages from inbox by subject, but if i search with a string like this: "Pedido de adição de danos à viatura sfaf", it does not work.</p>
  
  <pre><code>const inbox = require('inbox');
  
  const imap = inbox.createConnection(emailConfig.imapPort, emailConfig.imapHost, { secureConnection: true, auth: emailConfig.auth })
    .
    .
    .
  return new Promise&lt;number[]&gt;((resolve, reject) =&gt; {
      imap.search({ unseen: true, header: ["subject", subject] }, true, (err: any, uids: number[]) =&gt; {
          if (err) return reject(err);
          resolve(uids);
      })
  });
  </code></pre>
  
  <p>When i run with that subject i get this error: "Error searching messages"</p>
  
  <p>I'm reading from a Gmail account.
  Thanks in advance.</p>
  
  <p>[EDIT: I do the connect and openMailBox before]</p>