title: Fetch Post not working in redux-saga?
body: <p>I have the following code by using redux-saga to send a post request:</p>
  
  <pre><code>import {put, call, fork, takeEvery} from 'redux-saga/effects';
  import fetch from 'isomorphic-fetch';
  const url = 'xxx/api/posts';
  
  
  function* addPost(data) {
      try{
          const response = yield fetch(url, {
              method: 'POST',
              headers: {
                  'Accept': 'application/json, application/xml, text/plain, text/html, *.*',
                  'Content-Type': 'application/json; charset=utf-8'
              },
              body: JSON.stringify(data)
          });
          const id = yield response.json().id;
          yield put({type: types.ADD_POST, payload: {id, title, content }});
      }catch(e) {
          yield put({type: types.ERROR, payload: e});
      }
  }
  </code></pre>
  
  <p>But an ajax is sent with the 'OPTION' method, what's wrong with my code? Why it doesn't work?</p>