title: can't find symbol IonicErrorHandler exported from module
body: <p>I want to see how IonicErrorHandler could be useful to me. so I added this on top of my app.components.ts</p>
  
  <pre><code>import { NgModule, ErrorHandler } from '@angular/core';
  import { IonicApp, IonicModule ,IonicErrorHandler} from 'ionic-angular';
  </code></pre>
  
  <p>and this at bottom </p>
  
  <pre><code>  providers: [{provide: ErrorHandler, useClass: IonicErrorHandler}]
  </code></pre>
  
  <p>But I got this error on building .</p>
  
  <blockquote>
    <p>ngc error: Error: can't find symbol IonicErrorHandler exported from
    module
    /node_modules/ionic-angular/index.d.ts,
    resolving symbol AppModule in
    /.tmp/app/app.module.ts,
    resolving symbol AppModule in
    /.tmp/app/app.module.ts</p>
  </blockquote>