The inital loaded HTML does not contain anything of renderjs and gets added only after pageload.
Instead of registering init() for the DOMContentLoaded event directly, a deferred promise is used which gets resolve either by the event, or by a manual call of rJS.manualBootstrap().

Tests:
* injects rsvp/renderjs in a blank iframe
* makes sure renderjs is only present after it was injected
* calls manual bootstrap to initialzed renderjs
* creates small test gadget to ensure renderjs is working within the iframe (after bootstrap was executed)