Use babel@6.1.8 for CI

Author: Andrey Fedoseev

circle.yml

@@ -3,7 +3,7 @@ dependencies:
     - sudo apt-get install python2.7-dev python3.4-dev
     - npm install -g coffee-script@1.7.1
     - npm install -g less@1.7.4
-    - npm install -g babel@6.2.0
+    - npm install -g babel@6.1.8
     - npm install -g stylus@0.50.0
     - npm install -g handlebars@4.0.2
     - gem install sass -v 3.4.9