Fix the direction of replacement type checking
Add BuilderConfiguration for both parsing and canonicalization
Add Element.childElements and Element.descendantElements
Switch '%' and '%%' operators.  This reads better.
Support conversion of scala.xml.NodeSeq into Iterable[ChildSpec]
Remove old code which allowed for transformations that produced something other than a Document
Make transformer function take Nodes instead of NodeSpecs
Add Selection to preserve the document reference (for transformations) even when there are no nodes in the Iterable
Reenable ElementsTest and add more tests
seal Node traits