New example app: StudyNotes

Submitting my app ([StudyNotes](http://www.apstudynotes.org)) via pull request as requested by @jonathanong in https://github.com/visionmedia/expressjs.com/issues/89#issuecomment-30272706.

![studynotes 2x](https://f.cloud.github.com/assets/121766/1729985/09c19eb6-62cf-11e3-8ffb-3c50c079030e.png)