snabbdom-merge

This is a function to merge two snabbdom vnodes, vnode1 and vnode2, with the following behavior:
* Do a standard object merge on the 'props', 'class', 'style', 'attrs', and 'dataset', with the data in vnode2 getting precedence
* Chain event listener and hook functions together, with the function from vnode1 getting called first, then the function in vnode 2
* Eg if vnode1 is h('a', {on: {click: fn1}}) and vnode2 is h('a', {on: {click: fn2}}), then the merged vnode will call fn1, then fn2
* Concat together selector strings, preserving classnames.
* Eg if vnode1 is h('div.x') and vnode2 is h('div.y.z') then the merged vnode will be h('div.x.y.z')
* Concatenate the children of vnode1 with the children of vnode2

merge(vnode1, vnode2)

This function returns a brand new, merged vnode with the above behavior. vnode1 and vnode2 should have the same tag names.

_Example_

``js
var h = require('snabbdom/h').default
var merge = require('snabbdom-merge')

var sayhi = function(ev) { console.log('hi', ev) }
var saybye = function(ev) { console.log('bye', ev) }

var vnode1 = h('button.x', {attrs: {'data-x': 'x'}, on: {click: sayhi})
var vnode2 = h('button.y', {attrs: {'data-y': 'y'}, on: {click: saybye})

var merged = merge(vnode1, vnode2)

// Result:
//
// h('div.x.y', {
// attrs: {'data-x': 'x', 'data-y': 'y'}
// , on: {click: function(ev) { sayhi(ev); saybye(ev) }}
// }, [h('span', 'x'), h('span', 'y')])
``