fixed npm start

Author: caesar_chi

package.json

@@ -5,7 +5,7 @@
   "main": "index.js",
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1",
-    "start": "gitbook serve",
+    "start": "node_modules/.bin/gitbook serve",
     "build": "giik source book"
   },
   "authors": [