title: rx java obsever pojo model for change
body: <p>how use detect change POJO model?
  see sample</p>
  
  <pre><code>public class User {
       String firstName;
       String latsName;
  }
  </code></pre>
  
  <p>and</p>
  
  <pre><code>public void main(){
      User user = new User();
      user.setFirstName("rasoul");
  
      //detect change by rxJava or Rx android
  
  }
  </code></pre>
  
  <p>I need use rxjava to detect change model user</p>