Add replaceNode switch (#141)

* Add replaceNode switch

* Add test for replaceNode()

* Update TS definitions

lib/switches.js

@@ -26,6 +26,12 @@ module.exports = {
     this.onSwitch()
   },
 
+  // Equivalent to outerHTML(), but doesn't require switchElementsAlt() for <head> and <body>
+  replaceNode: function(oldEl, newEl) {
+    oldEl.parentNode.replaceChild(newEl, oldEl)
+    this.onSwitch()
+  },
+
   sideBySide: function(oldEl, newEl, options, switchOptions) {
     var forEach = Array.prototype.forEach
     var elsToRemove = []