update gulp-sass for node v4.x.x

Author: Yago

package.json

@@ -22,7 +22,7 @@
     "gulp-minify-css": "^0.3.7",
     "gulp-notify": "^1.5.0",
     "gulp-rename": "^1.2.0",
-    "gulp-sass": "^1.3.2",
+    "gulp-sass": "^2.0.4",
     "gulp-shell": "^0.2.9",
     "gulp-sourcemaps": "^1.3.0",
     "gulp-svgmin": "^0.4.6",