upgrade chrome version in circleci

circle.yml

 machine:
   node:
     version: 6.0.0
+  post:
+    - wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo apt-key add -
+    - sudo sh -c 'echo "deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main" >> /etc/apt/sources.list.d/google.list'
+    - sudo apt-get update
+    - sudo apt-get install google-chrome-stable
 
 dependencies:
   post: