Specify Node.js version >= 0.10.32 (but <0.12) in package.json

On Azure, only Node.js versions up to 0.10.32 are installed at the
moment (current release is 0.12.x). Note that this is for documentation
only, as npm doesn't seem to enforce this (even with engineStrict: true),
see npm/npm#3672.

package.json

@@ -20,5 +20,6 @@
   "dependencies": {
     "express": "^4.11.2",
     "serve-static": "^1.8.1"
-  }
+  },
+  "engines" : { "node" : ">=0.10.32 <0.12" }
 }