Change milestone version to 2.0-M4u1.

Fix a bug in MemoizationList.

Properly handle the case when source.get() in force() causes forget().

Update Milestone version to 2.0-M3.

Add method MemoizationList.getMemoizedCount().

Add EventStreams.animationTicks() and FPSDemo.

Move lazy binding functionality to ObservableBase.

Leaving nothing left in LazilyBoundStream => deleting.

Better support for ObservableList changes:

* Add ListChange, TransientListChange and MaterializedListChange interfaces.
  These provide a simpler model for list changes than
  javafx.collections.ListChangeListener.Change.
* Expose ListChangeAccumulator.
* Add EventStreams.simpleChangesOf(ObservableList) factory method.

Print errors to stderr if no handler provided.

Rename watch(onEvent, onError) to subscribe(...).

Implement subscribe(onEvent) as
    subscribe(onEvent, Throwable::printStackTrace)

Update version to 1.3.

Register error handlers before subscribers.