title: How to use FCM in ionic v1
body: <p>I am new in ionic, I want to know how to use FCM in ionic v1 project Please help me. I am using Cordova-plugin-fcm.
  At first, i am installing this plugin in my project using this comment
  "ionic Cordova plugin add Cordova-plugin-fcm"</p>
  
  <pre><code>FCMPlugin.getToken(
  function (token) {
      alert('Token: ' + token);
      console.log('Token: ' + token);
  },
  function (err) {
      alert('error retrieving token: ' + token);
      console.log('error retrieving token: ' + err);
  }
  </code></pre>
  
  <p>);</p>
  
  <p>then using this code in my app.js,  $ionicPlatform.ready()</p>
  
  <p>now the error is showing my browser console</p>
  
  <pre><code>FCMPlugin is not defined
  </code></pre>
  
  <p>please help me</p>