Bugfix: event attacher for old IEs was broken, didn't return a function.
Typofix, no need to check if recipient is set in this case, it won't be.
Settings that.communicator = that was incorrect.
Moreover, what it was meant to be, that.sender.communicator = that, was
unnecessary, since the sender does not need direct access to its
communicator.
Adding ability to communicate with instantiated object/communicator.
More flexible target_origin setting in specs.
Means these spces can be run on different hosts and still pass.
Stringify objects and arrays for postMessage.
This addresses the issue with older IEs that can only pass strings with
postMessage. We could do feature detection, but that would be hairy
since it would have to be asynchronous, and we could do browser
detection, but that's ugly.