js_of_ocaml1.5dev installs as the js_of_ocaml.compiler subpackage now

As of ocsigen/js_of_ocaml@7d15343b2a5b9af85210ba1a8279f7bb107af43d
Installation: create directory first and make ipython optional

...since iocaml no longer requires ipython to be installed at all (!)
Merge pull request #3 from avsm/fix-ocamlfind-packages

Fix ocamlfind packages and installation