title: Await not parsed in esprima 4.0.1
body: <p>Can't get the <a href="https://github.com/jquery/esprima" rel="nofollow noreferrer">esprima</a> 4.0.1 parser to work with 'await'.  Having difficult times to find the relevant options that can be passed into the parse function for 'await', if that is possible.</p>
  
  <h3>Steps to reproduce</h3>
  
  <pre><code>const esprima = require('esprima');
  esprima.parse("await function_call()")
  </code></pre>
  
  <h3>Expected output</h3>
  
  <p>Describing the code structure containing the await call</p>
  
  <h3>Actual output</h3>
  
  <p>Error: Line 1: Unexpected identifier</p>