Ehancement #2365 : Add markup root directly in ReactMount cache

@syranide Could you check this ?
I wanted to add checking on node parameter because we need a HTML element, but I'm not sure if this is the best way of doing this.
Also, if this okay, I might write some test for ReactMount.cacheNodeById.
But is this problem still here, even if I avoided to use getReactRootID ?
In my PR I use getID on the new node (in ```ReactDOMIDOperations.dangerouslyReplaceNodeWithMarkupByID``` ) , but I don't explicitly remove the old node from the cache. So I wanted to know if it's handled with my modifications ^^