Avoid calling getElementChecksum if not needed

If there's no checksum in serialized, there's no need to call getElementChecksum(rootNode).
Also, getElementChecksum(rootNode) is called once more if there is checksum in serialized.
Updated README with Google Code project URL.
Merge pull request #211 from YSYoon/master

Avoid calling getElementChecksum if not needed
Merge remote-tracking branch 'upstream/master'

merge original rep into my for of rangy