Reintroduce erlang_js.

I had some issues between R16 and R15 with starting the deps of habanero. This
commit introduces a recursive form of the common ensure_deps and relies on a
static habanero.app. That is not _strictly_ necessary but it does make debugging
this sort of startup issue more simple.

Signed-off-by: Brian L. Troutwine <brian.troutwine@adroll.com>