add client example using conduit and lwt
hookup client example
regenerate
spice up demo server with tls certificate and key
Add sexp onverters for Conduit and Lwt client and server modules
Merge branch 'client-lwt-example' of git://github.com/hannesm/ocaml-cohttp

Conflicts:
	setup.ml
Add `Cohttp_lwt_unix_debug` which lets libraries control the debugging
output from Cohttp.  Previously the only way to do this was to set the
`COHTTP_DEBUG` environment variable at the program start.

This puts a very slight performance hit on the read/write functions
since they need to check the debug variable now, but it's not at all
significant in a localhost test.
Port cohttp_client_lwt to use Cmdliner and be more curl-like
Rename cohttp_client_lwt to cohttp-curl-lwt to match the async version