Remove type warning by letting compiler know collection is a List
Renamed Node.elements -> Node.children

Following updates in dart:html
Renamed outerHTML -> outerHtml, innerHTML -> innerHtml

following updates in dart:html
Moved id from Node to Element
Node: added hasChildNodes() and contains(Node)

aligning with dart:html
Merge pull request #56 from kevmoo/master

Updating DOM apis to align with deprecations in dart:html