Merge pull request #53 from dstockwell/test-harness

Test harness updates
Support animation of visibility.
Merge pull request #54 from dstockwell/visibility-type

Support animation of visibility
Fix style in tests
Merge pull request #55 from steveblock/testStyle

Fix style in tests
Fix bad merge
Merge pull request #56 from dstockwell/fix-everything

Fix bad merge
Simplify AnimListMixin
Clear parent group when children are removed.
Use isDefined instead of exists
Correctly support splice with the variadic newItem argument
Merge pull request #2 from dstockwell/simplify-list-mixin

Simplify AnimListMixin
Use textContent instead of innerText
Visibility is just a specialization of non-numeric
Merge pull request #59 from dstockwell/simplify-visibility

Visibility is just a specialization of non-numeric
Remove superfluous window scoping
Move compositor out of DEFAULT_GROUP to global scope

There's no particualr reason why the compositor should be part of
DEFAULT_GROUP, and DEFAULT_GROUP will be going away with the upcoming
refactoring for TimeSources, so move it now.
Fix test-svg-anim.html
More style fixes
Merge pull request #61 from steveblock/style

More clean-up in preparation for TimeSources