a quick patch to remove unneeded (locking ...) around SSE channels

The current code locks channels in order to preserve ordering when sending SSE events. This patch removes these locks and instead mk-data to construct a single large message that contains all data. There really should never be a time when we'd need to lock a channel. 

Eventually this could possibly be improved by using a transducer in the channel that contains a call to flatmap. This would allow for vector messages to be spliced in, while preserving ordering. But for now this patch should be good enough.