Better Cleanup

To enable better cleanup i added cleanupGently and cleanupAll. cleanupGently is your original cleanup happening every 30s. I made this also callable via Jsonary.render.cleanupGently(). cleanupAll is also callable via Jsonary.render.cleanupAll() and should be called only when your shure that there should be no more Jsonary objects.

see issue #52 for more details...
Ognian