sass version updated

package.json

@@ -71,7 +71,7 @@
     "gulp-imagemin": "~2.4.0",
     "gulp-postcss": "^6.0.1",
     "gulp-rename": "^1.2.2",
-    "gulp-sass": "^2.1.1",
+    "gulp-sass": "^3.1.0",
     "gulp-uglify": "~1.5.0",
     "html-minify-loader": "~1.1.0",
     "istanbul": "~0.4.2",