title: Promisify Joi: compile is undefined
body: <p>I want to promisify Joi.validate.</p>
  
  <p>The original function is:</p>
  
  <pre><code>Joi.validate(message, schema, (err, success) =&gt; {})
  </code></pre>
  
  <p>I tried to do:</p>
  
  <pre><code>const Joi = require('joi');
  const Promise = require('bluebird');
  const validate = Promise.promisify(Joi.validate);
  </code></pre>
  
  <p>And I call with:</p>
  
  <pre><code>validate(message, schema)
  .then(() =&gt; console.log('ok'))
  .catch(err =&gt; console.log('ERRRR', err.message));
  </code></pre>
  
  <p>But i receive this error:</p>
  
  <pre><code>Cannot read property 'compile' of undefined
  </code></pre>
  
  <p>Do you know how I can achieve it ?
  Thank you</p>