better 'dispose' handling in 'removeFromParent' (closes #330)
EventDispatcher: optimized access of listener[i] in removeEventListener()
Merge pull request #334 from joshtynjala/removeEventListener

EventDispatcher: optimized access of listener[i] in removeEventListener()
now using a minimum texture size for filters (closes #312)

to avoid constant texture recreation when filter region gets small.
auto-trimming number of used quad batches (closes #329)
now using a stable sort algorithm for 'sortChildren' (closes #304)

It's a merge sort algorithm that doesn't do any allocations while it runs.