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