Missing push notifications for all but first device when sending through Delayed::Job

Not sure why this is, or why my fix fixes this problem (or even whether anyone else has encountered this), but I've noticed that when I have multiple devices queued up for push notifications in a Delayed::Job, the PRX Master branch doesn't seem to successfully send notifications to any device beyond the first one. At least that was my experience on Heroku.

I was able to solve this problem by adding a sleep() instruction for a VERY small fraction of time (specifically 0.00000001). If no one else has experienced this problem, I'd recommend rejecting my pull request. Also, if there's some better solution to this, I'd appreciate knowing about it. If, however, there are others who have experienced this issue, and no solution has been found, I recommend this, as it is simple, and does not seem to have singificant drawbacks.