updated for new express functionality but not quite there (routing)

[step21]

Hi,

so when trying it, it was broken for me as newer express wanted to use connect + 'middleware' instead of stuff before integrated into express. It starts and kind of works, but so far 'addPost' for example doesn't do anything, but there are no errors either. If you think this update could be incorporate when it's done and could take a look, I can do a pull request/link my repo.