How can exclude `___.stories.js`files from tests? This is my component structure: <img width="182" alt="screen shot 2017-10-13 at 1 02 37 pm" src="https://user-images.githubusercontent.com/371939/31555286-da537ea8-b016-11e7-9265-d2ee86a7dbce.png"> and this is the coverage report: <img width="736" alt="screen shot 2017-10-13 at 1 03 22 pm" src="https://user-images.githubusercontent.com/371939/31555302-ee86e0cc-b016-11e7-93af-236ff69f1640.png">