Fix continual allocation of auto-releaseable NSDate objects

The startInterval method of the AudioPlayer module causes a
continually increasing number of NSDate objects to be
allocated. The auto-release pool which wraps this code doesn't
drain frequently enough causing an application's memory
footprint to grow by roughly a megabyte every 5 minutes.
Merge pull request #1 from gangverk/bugfix/continuous-date-allocation

Fix continual allocation of auto-releaseable NSDate objects