[FIX] correctly display JS stack frames in phantomjs runner

[FIX] correctly display JS stack frames in phantomjs runner

altered reporting to handle and deserialize JSON if JSON-deserializable. Can't
just send multiple lines as driver currently does not handle multiple lines of
message... Yeah turns out having a JSON-based protocol between phantomjs and
the python runner allowed multiple lines in messages, who'd have thought eh?

bzr revid: xmo@openerp.com-20140219123850-0h0upb3x33j7leqk