add gulp watch

package.json

@@ -30,13 +30,13 @@
     "gulp-stylus": "1.3.3",
     "gulp-uglify": "1.0.1",
     "gulp-util": "3.0.x",
+    "gulp-watch": "1.1.0",
     "gulp-webserver": "0.8.3",
     "merge-stream": "0.1.6",
     "require-dir": "0.1.0",
     "node.extend": "1.1.2",
     "nunjucks": "1.0.x",
     "through2": "0.6.2",
-    "underscore": "1.7.x",
     "stylus": "0.32.x",
     "yargs": "1.3.1"
   },