Document Pedestal for speed demons

[mtnygard]

@ohpauleez has gotten some great performance out of Pedestal apps. We need a guide that shows everyone how to do this.

The "fast-pedestal" sample app is there. Readers could benefit from a walkthrough doc that explains the differences from a default (i.e., template-generated) service.

Paul also has code in a private repo (https://github.com/cognitect-labs/FrameworkBenchmarks-internal/tree/master/frameworks/Clojure/pedestal/src/pedestal) that @mtnygard can use to write a guide.

[ohpauleez]

The guide should also mention the three kinds of requests that Pedestal has to offer (map, lazy, and zero-copy), as well as the strategy for making your own custom request type (common with hand-created chain-providers).

It's also important that we talk about the Router performance and how the route table affects possible optimizations (ie: the MapTree router can only be used if wildcard and param URLs are avoided).