Gulp: Avoid re-building unchanged files by caching the results

package.json

@@ -8,17 +8,18 @@
   "license": "GPL",
   "devDependencies": {
     "gulp": "~3.9.1",
-    "gulp-sass": "~2.3.1",
     "gulp-autoprefixer": "~2.3.1",
+    "gulp-cached": "~1.1.0",
+    "gulp-chmod": "~1.3.0",
+    "gulp-concat": "~2.6.0",
     "gulp-if": "^2.0.1",
     "gulp-jade": "~1.1.0",
-    "gulp-sourcemaps": "~1.6.0",
-    "gulp-plumber": "~1.1.0",
     "gulp-livereload": "~3.8.1",
-    "gulp-concat": "~2.6.0",
-    "gulp-uglify": "~1.5.3",
+    "gulp-plumber": "~1.1.0",
     "gulp-rename": "~1.2.2",
-    "gulp-chmod": "~1.3.0",
+    "gulp-sass": "~2.3.1",
+    "gulp-sourcemaps": "~1.6.0",
+    "gulp-uglify": "~1.5.3",
     "minimist": "^1.2.0"
   }
 }