Implement JSON file based asset pipeline

Adds manifest.json which contains all of the mappings for the assets
ref: https://github.com/roots/roots/pull/1138#issuecomment-62593715

Prune and update NPM deps

package.json

@@ -21,27 +21,30 @@
     "node": ">= 0.10.0"
   },
   "devDependencies": {
+    "del": "^0.1.3",
     "gulp": "^3.8.10",
-    "gulp-autoprefixer": "^0.0.7",
-    "gulp-clean": "^0.3.1",
+    "gulp-autoprefixer": "^2.0.0",
     "gulp-concat": "^2.3.4",
-    "gulp-filter": "^0.4.1",
-    "gulp-grunt": "^0.5.2",
-    "gulp-imagemin": "^0.6.0",
+    "gulp-flatten": "0.0.4",
+    "gulp-if": "^1.2.5",
+    "gulp-imagemin": "^2.0.0",
     "gulp-jshint": "^1.8.4",
     "gulp-less": "^1.3.3",
     "gulp-livereload": "^2.1.0",
-    "gulp-load-plugins": "^0.5.0",
-    "gulp-minify-css": "^0.3.7",
+    "gulp-load-plugins": "^0.7.1",
     "gulp-plumber": "^0.6.3",
     "gulp-rename": "^1.2.0",
     "gulp-rev": "^2.0.1",
+    "gulp-sass": "^1.1.0",
     "gulp-sourcemaps": "^1.1.1",
-    "gulp-uglify": "^0.3.1",
-    "imagemin-pngcrush": "^1.0.0",
-    "jquery": "1.11.1",
-    "jshint-stylish": "^0.4.0",
+    "gulp-uglify": "^1.0.1",
+    "imagemin-pngcrush": "^4.0.0",
+    "jshint-stylish": "^1.0.0",
+    "lazypipe": "^0.2.2",
     "lodash": "^2.4.1",
-    "main-bower-files": "^1.0.1"
+    "main-bower-files": "^2.4.0",
+    "object-path": "^0.8.0",
+    "traverse": "^0.6.6",
+    "wiredep": "^2.1.0"
   }
 }