Update Express from 3.4.0 to 3.4.7

This release includes lots of updates to Connect, the middleware Express is based on. It also adds a `res.vary()` method to set the `Vary` header and a load of other bugfixes.

- https://github.com/visionmedia/express/compare/3.4.0...3.4.7
- https://github.com/visionmedia/express/blob/3.4.7/History.md