fix: add tonic demo

Author: remy

example.js

@@ -0,0 +1,14 @@
+var undefsafe = require('undefsafe');
+
+var object = {
+  a: {
+    b: {
+      c: 1,
+      d: [1,2,3],
+      e: 'remy'
+    }
+  }
+};
+
+console.log(undefsafe(object, 'a.b.e')); // "remy"
+console.log(undefsafe(object, 'a.b.not.found')); // undefined

package.json

@@ -3,6 +3,7 @@
   "version": "0.0.3",
   "description": "Undefined safe way of extracting object properties",
   "main": "lib/undefsafe.js",
+  "tonicExampleFilename": "example.js",
   "directories": {
     "test": "test"
   },