Support for simple begin and end times

Times may be specified using attributes, or using
beginElement/endElement DOM calls that are exposed by the
SVGAnimationElement IDL.

Automated tests stil to be added.
Retire createAnimationRecord

The logic in createAnimationRecord has been moved to the AnimationRecord
constructor.

Add example with list of begin and end times
For now, simple-list-begin-end.html is a manual test.
Merge pull request #20 from ewilligers/begin-end-times

Support for simple begin and end times