Express 4.x

Increasingly, I feel that `lib/server` and the CLI executable should be separated from the rest of the library (`combohandler-server`?), as it is itself just a consumer of the middleware. It's burdening those whole only ever use the library as middleware with all of express, etc.

The changes herein are largely explained by the [Migrating from 3.x to 4.x](https://github.com/visionmedia/express/wiki/Migrating-from-3.x-to-4.x) wiki.