Keyframe duration is an integer, not a decimal

(duration is a frame-based measurement, not a time-based one)
Append empty keyframe to layers with "truncated" timelines (fixes #86)

A layer should not display anything beyond its last keyframe. During
export, we just slap an extra empty keyframe onto any layer that has a
shorter duration than its parent movie, and that doesn't already end
in an empty keyframe.
Fix off-by-1 in empty keyframe creation
Better data encapsulation in Layer
Solve the "empty layer frames" issue in the runtime, not the exporter

Instead of adding empty keyframes to Layers at export time, we do the
right thing at runtime and swap in an empty sprite when a layer is asked
to draw a frame past the end of its frame count.

This is closer in spirit to what Flash does, and doesn't require assets
to be re-exported.

(It does require that other runtimes be updated in order to take
advantage of the fix, of course.)
When adding a child movie to a layer, reset its timeline
Consecutive keyframes with the same library item share DisplayObjects
remove unused variable
react-as3 1.0 is published
build against Starling 1.4
update Flash Builder runtime project
Flump version 1.2
prepare for 1.3 development