Connect 3

https://github.com/senchalabs/connect/wiki/Connect-3.0

When? Who knows. We'll leave multipart deprecated for a while so people aren't like "WTF U REMOVED MULTIPART?!"

To do:

- [x] alias `.headersSent` as `.headerSent`
- [x] Remove multipart middleware
- [x] Remove limit middleware
- [x] Remove staticCache
- [x] Remove the pause utility
- [ ] fix this branch
- [ ] switch cookies to [jed/cookies](https://github.com/jed/cookies) and [jed/keygrip](https://github.com/jed/keygrip) (including sessions and cookie sessions)
- [ ] remove `cookieParser`, create a `cookies` middleware instead.
- [ ] switch basic auth to [basic-auth](https://github.com/visionmedia/node-basic-auth)
- [ ] fix sessions - maybe defer this to 4.x. sessions is too complicated.
- [ ] document alternative middleware
- [ ] update docs