Document and deprecate Lwt_pqueue
Document and deprecate Lwt_pqueue

Resolves #135.

[skip ci]

rneswold/lwt,ocsigen/lwt,rgrinberg/lwt,c-cube/lwt,rneswold/lwt,rgrinberg/lwt,ocsigen/lwt,c-cube/lwt,c-cube/lwt,rneswold/lwt,rgrinberg/lwt,ocsigen/lwt,rgrinberg/lwt