Add an example that renders a simple fractal

This works at resolutions where simplification is significantly reducing the number of points in the line.  At high resolutions, navigation becomes unresponsive.  Limiting draw instructions to a replay group's extent will fix this.
Keep track of max extent for replay
Determining coordinate relationship to extent
Testing segment intersection with extent

If needed, this function can be modified to take two additional coorinates that will be set to the intersection points.
Skip coordinates that don't affect the rendered extent

Segments that intersect the replay group's extent are drawn.  Any segment that represents a change in coordinate-extent relationship is drawn.  This maintains the left/right relationship (or cross product) between points in the rendered extent and every rendered segment.

Still left undone: clip the replay group's rendering to the max extent.
Clip to max extent
Function for applying a 2d transform to an extent
Support minPointsPerRing and default to 3
Transform extent coordinates before clipping
Set overlay map in 'add' and 'remove' event handler
Set interaction map in 'add' and 'remove' event handler
Set control map in 'add' and 'remove' event handler
Dispatch 'render' event in renderer.canvas.VectorLayer

The context property of the event only contains the vector rendering.
Add ol.layer.Heatmap class and example
Don't use Uint32Array for IE compatibility
Merge pull request #1806 from fredj/overlays-events

Set map in 'add' and 'remove' event handler
Rename ol.structs.RBush#getAllInExtent to getInExtent
Merge pull request #1810 from twpayne/rbush-get-in-extent

Rename ol.structs.RBush#getAllInExtent to getInExtent
Merge pull request #1687 from fredj/ol.layer.Heatmap

Add ol.layer.heatmap
Add explicit includes/excludes to jsdoc config.