Untracking data/, fixing default ports.

Having anything in `data/` made stuff not work. I've thus removed the entire `data/` folder from cache and put in .gitignore. I also fixed a bug I introduced by not putting `(process.env.PORT || 3333)` in parentheses (durr). See [#9](https://github.com/flatsheet/flatsheet/issues/9#issuecomment-55057278).

**Be forewarned!** (If my knowledge of how `git rm --cached` works is accurate) — By untracking and removing `data/`, your `data/` folder *WILL* be deleted upon next pull! Its contents should be backed up and replaced after the pull!