add code coverage

Author: jcouyang

circle.yml

@@ -11,6 +11,7 @@ dependencies:
 test:
   post:
     - cd examples/todomvc && npm install && npm test
+    - bash <(curl -s https://codecov.io/bash)
 deployment:
   production:
     tag: /v[0-9]+(\.[0-9]+)*/