title: Karma, PhantomJS and es6 Promises
body: <p>I am writing a JavaScript library that uses the new es6 promises. I can test the library in Firefox because promises are defined. However, when I try to test my code with Karma and PhantomJS, I get the error <code>Can't find variable: Promise.</code>. I am guessing this is because the PhantomJS browser doesn't support es6 promises yet.</p>
  
  <p>How can I configure Karma to bring in the polyfill for promises?</p>