Update sample to use published version reference

- Change intuit-oauth dependency from 'file:../' to '^4.2.2'
- Prepares sample app for production use with published npm package
- Users can install the sample once version 4.2.2 is published to npm

Author: rgupta24723

sample/package.json

@@ -17,7 +17,7 @@
     "ejs": "^3.1.9",
     "express": "^4.14.0",
     "express-session": "^1.14.2",
-    "intuit-oauth": "file:../",
+    "intuit-oauth": "^4.2.2",
     "ngrok": "^5.0.0-beta.2",
     "path": "^0.12.7"
   },