title: Get custom attributes from material ui text field inside onChangeHandler
body: <p>Hi I am using react and material ui.</p>
  
  <p>The markup for textfield is something like this</p>
  
  <pre><code>&lt;TextField                    
      floatingLabelText="Email"
      onChange={this.props.onChange}
      ref="email"
      customAttr="customValue"
      errorText = {this.props.errors.email}
  /&gt;
  </code></pre>
  
  <p>My onChange handler is below </p>
  
  <pre><code>function onChange(e) {
     var customVal = e.target.getAttribute("customAttr");
     alert(customVal);  //undefined
  }
  </code></pre>
  
  <p>I want to get the value of the my custom attribute when using material ui.</p>
  
  <p>Please help!!</p>