added es6-promise to npm package dependencies so it installs upon npm…

… run setup

package.json

@@ -8,22 +8,23 @@
   },
   "devDependencies": {
     "browser-sync": "~2.7.4",
-    "imagemin-pngcrush": "~4.1.0",
-    "node-sass": "^3.4.1",
+    "es6-promise": "^4.0.5",
     "gulp": "~3.9.0",
     "gulp-autoprefixer": "^3.1.0",
     "gulp-concat": "^2.6.0",
     "gulp-imagemin": "~2.2.1",
+    "gulp-jshint": "~2.0.0",
     "gulp-notify": "^2.2.0",
     "gulp-plumber": "~1.0.1",
     "gulp-rename": "^1.2.2",
     "gulp-sass": "~2.0.1",
     "gulp-sass-glob": "0.0.2",
+    "gulp-scss-lint": "~0.3.9",
     "gulp-shell": "~0.4.1",
     "gulp-sourcemaps": "^1.6.0",
     "gulp-uglify": "^1.5.1",
-    "gulp-scss-lint": "~0.3.9",
+    "imagemin-pngcrush": "~4.1.0",
     "jshint": "~2.9.1",
-    "gulp-jshint": "~2.0.0"
+    "node-sass": "^3.4.1"
   }
 }