title: POST dosn't work in yii2 restful API
body: <p>I used yii2 restful API  explained hear:
  <a href="http://www.yiiframework.com/doc-2.0/guide-rest-quick-start.html" rel="nofollow">http://www.yiiframework.com/doc-2.0/guide-rest-quick-start.html</a> </p>
  
  <p>and in CURL it works correctly for GET and DELETE.
  but when i use this in CURL:</p>
  
  <pre><code>curl -i -H "Accept:application/json" -H "Content-Type:application/json" 
  -XPOST "my localhost path/customers"
  -d '{"name": "xxxx", "family": "xxxx","mobile":"xxxxx","home":"xxxxx","work":"xxxx"}'
  </code></pre>
  
  <p>It inserts only auto increment field "id", in my table 'customer' and other fields in my database is empty!</p>