Add isSameNode check.

[kj]

[Yosh]

perfect, yeah we need this - should be straight forward to implement I reckon

• spec https://developer.mozilla.org/en/docs/Web/API/Node/isSameNode
• code in morphdom https://github.com/patrick-steele-idem/morphdom/search?utf8=%E2%9C%93&q=issamenode

[kj]

on it.