Problems with VirtualDom.map

[evancz]

There are a couple issues reported about VirtualDom.map. I am collecting them here so that it is easier to think about them together.

• switching between map f node and node should reuse DOM - #14, #35
• Bad interaction between lazy and map can cause a crash - #73
• Bad interaction between lazy and onblur can break message tagging - #103, https://github.com/elm-lang/html/issues/119
• using elm_event_node_ref may be unreliable in IE11? - #101