include underscore as a dependency for npm

package.json

 {
-  "author": "Hakim El Hattab",
-  "name": "Reveal.js",
-  "description": "HTML5 Slideware with Presenter Notes",
-  "version": "1.5.0",
-  "repository": {
-    "type": "git",
-    "url": "git://github.com/hakimel/reveal.js.git"
-  },
-  "engines": {
-    "node": "~0.6.8"
-  },
-  "dependencies": {
-    "express" : "2.5.9",
-    "socket.io" : "0.9.6",
-    "mustache" : "0.4.0"
-  },
-  "devDependencies": {}
+	"author": "Hakim El Hattab",
+	"name": "reveal.js",
+	"description": "HTML5 Slideware with Presenter Notes",
+	"version": "1.5.0",
+	"repository": {
+		"type": "git",
+		"url": "git://github.com/hakimel/reveal.js.git"
+	},
+	"engines": {
+		"node": "~0.6.8"
+	},
+	"dependencies": {
+		"underscore" : "1.3.3",
+		"express" : "2.5.9",
+		"socket.io" : "0.9.6",
+		"mustache" : "0.4.0"
+	},
+	"devDependencies": {}
 }