Add skeleton Express application

Summary: I have set up a basic Express application using the MVC pattern. You should check that you can get it running first before we continue on our awesomeness.

Test Plan:
- Run `git clone git@github.com:interslice/cronator.git`
- Run `arc patch D1`
- Install Node.
- Install Mongo.
- Run `npm install` on the root directory of this project.
- Run `npm start`.
- Go to `http://localhost:3000` on your browser.
- You should get a message along the lines of "Welcome to Cronator".
- Go to some random page, e.g. `http://localhost:3000/thai-smells`.
- You should get a message that says "Page Not Found"

Reviewers: Kiante

Reviewed By: Kiante

CC: DuBistKomisch

Differential Revision: http://phabricator.interslice.in/D1