Don't use Express for lambdas

[ericclemmons]

This would be a breaking change, but using express means routes aren't compatible with plain lambads (like now).

• Examples will need to use res.end and res.writeHead.
• Any complex examples/routes can still depend on express as a dependency.
• Params can be added to req.query via routing: https://spectrum.chat/zeit/now/are-url-parameters-possible-with-v2-routing~e1fec1df-09ff-4614-b031-4a0279b84bae