Optimize merging list of nodes

[mrroman]

Currently merger procedure:

1. Checks if number of child nodes is the same as number of views. If there are more views it creates new one(s).
2. Goes through the list and if the child node's connected view is different than merged view, it recreates it completely.

It is wrong because when someone adds view at the top of the list, child nodes are all rewritten nevertheless their views weren't changed. We can optimize it like React does it by adding key property to El and use it to merge child nodes.