Change Body.map to use a non-labelled type to fit the Lwt style better

The Async Body is still left labelled.

Suggested in #200
Merge pull request #215 from avsm/master

Server.make should take a final unit argument due to the optional label
Merge pull request #214 from mirage/body-map

Change Body.map to use a non-labelled type to fit the Lwt style better
update .merlin

* keep up with the cohttp -> lib rename
* add cmdliner
simplify expression in bin/lwt_server
Lwt_unix.run is deprecated

Lwt_main.run should be used
Merge pull request #216 from rgrinberg/merlin_update

Merlin update
Merge pull request #217 from rgrinberg/remove_lwt_unix_run

Remove Lwt_unix.run
improve ocamldoc of Cohttp.S