"Try everything" HTTP server script

[colindean]

https://gist.github.com/willurd/5720255 documents a bunch of ways to start a simple static server. I think it'd be useful to have a command httpserve that, well, tries everything. It'd have some flags that would exclude options, e.g. --multithreaded would remove Python's http.server and Ruby's webrick from consideration because they are single-threaded and couldn't handle multiple downloads simultaneously.

This could end up running redbean if added in #27 or miniserve if it's available.

[colindean]

I added https://github.com/eliben/static-server to serve in 1258701