Basic type definitions for express 4.x

*I'm still working on this. I'm making the PR so that other people can help if interested*

This pull request updates the type definitions for express 4.0. The old type definitions and tests are now on express-3.1.0* on the express folder.

The main change on express 4 is that it moves all the middleware to separate packages. I've added some of these packages but there are still some more. Hopefully writing type definitions for them will be very simple.