Fix intermittent event triggering failures.
Fix intermittent event triggering failures.

It seems that stringByAddingPercentEscapesUsingEncoding is buggy and wasn't URL
escaping + characters which meant any sigs with a + were failing.
lukeredpath/libPusher,alloy/libPusher,alloy/libPusher,LoyoChengdu/libPusher,andreaperizzato/libPusher,lukeredpath/libPusher,hamchapman/libPusher,alloy/libPusher,hamchapman/libPusher,LoyoChengdu/libPusher,hamchapman/libPusher,LoyoChengdu/libPusher,alloy/libPusher,lukeredpath/libPusher,alignd/libPusher,alignd/libPusher,lukeredpath/libPusher,hamchapman/libPusher,andreaperizzato/libPusher,LoyoChengdu/libPusher,alignd/libPusher,andreaperizzato/libPusher,andreaperizzato/libPusher,alignd/libPusher