add a test for Cohttp_lwt_xhr
Remove Yojson.  Display response.
Test OCaml 4.02 and new OPAM 1.2 as well
Merge branch 'js-xhr' of git://github.com/andrewray/ocaml-cohttp into v0.6

Conflicts:
	_tags
	js/cohttp_lwt_xhr.mli
	setup.ml