title: how to setstate after saga async request
body: <p>I'm using redux-saga in my project. 
  I used redux-thunk before, so i can't setState ends of some async request. like</p>
  
  <pre><code>this.props.thunkAsync()
    .then(){
      this.setState({ '' });
    }
  </code></pre>
  
  <p>Since thunk returns promise, i could use 'then'.
  But i can't do this with saga, because saga doesn't return promise.
  So i did it in componentWillReceiveProps by checking flag props (like REQUEST_SUCCESS,REQUEST_WAITING...) has been changed. 
  I think it's not good way to solve this problem.</p>
  
  <p>So.. My question is how can i do some works when async request ends in redux-saga!</p>