Fixed build issue on Node 7

Fixed a build issue on Node 7 caused by the following issue:

sass/node-sass#1766

package.json

@@ -15,7 +15,6 @@
   },
   "devDependencies": {
     "bower": "^1.7.7",
-    "highlight.js": "^9.7.0",
     "grunt": "^1.0.1",
     "grunt-build-control": "^0.7.0",
     "grunt-cli": "^1.2.0",
@@ -27,18 +26,20 @@
     "grunt-contrib-watch": "^1.0.0",
     "grunt-npmcopy": "^0.1.0",
     "grunt-sass": "^1.1.0",
-    "grunt-shell": "^1.1.2",
+    "grunt-shell": "^2.1.0",
     "handlebars": "^4.0.5",
     "helper-moment": "0.1.0",
+    "highlight.js": "^9.7.0",
     "metalsmith": "^2.1.0",
-    "metalsmith-collections": "^0.7.0",
+    "metalsmith-collections": "^0.9.0",
     "metalsmith-ignore": "^0.1.2",
     "metalsmith-layouts": "^1.6.4",
     "metalsmith-markdown": "^0.2.1",
-    "metalsmith-metallic": "^1.0.0",
+    "metalsmith-metallic": "^2.0.1",
     "metalsmith-path": "^0.2.0",
     "metalsmith-publish": "^0.1.4",
-    "metalsmith-register-helpers": "^0.1.2"
+    "metalsmith-register-helpers": "^0.2.0",
+    "node-sass": "^3.13.0"
   },
   "scripts": {
     "install": "bower install",