chore(build): use node-sass instead of ruby sass

.travis.yml

@@ -12,8 +12,6 @@ notifications:
       secure: mkHfRTsuxidtOOORbJJ0Jspb/DSa8jAiQwWWUljqLwefy1p4HGC9P/rLdXXg3vsjiulCzyjEkfvDWAHXvu34GhGWfQuD8U140Fon1Os3AO5Hbme+yRmjXmTcgH8XetSLQufyBBMqXHMd6o1tkxXql1p54G1IShhgAdPNe76d5ZE=
 
 before_install:
-- gem update --system
-- gem install sass
 - npm install -g grunt-cli
 
 before_script:

package.json

@@ -10,11 +10,11 @@
     "grunt-contrib-copy": "~0.5.0",
     "grunt-contrib-cssmin": "~0.7.0",
     "grunt-contrib-jshint": "~0.8.0",
-    "grunt-contrib-sass": "~0.7.2",
     "grunt-contrib-uglify": "~0.3.2",
     "grunt-contrib-watch": "~0.5.3",
     "grunt-ddescribe-iit": "0.0.4",
     "grunt-merge-conflict": "0.0.2",
+    "grunt-sass": "~0.10.0",
     "grunt-string-replace": "~0.2.7",
     "karma": "~0.11.13",
     "karma-chrome-launcher": "~0.1.2",