fix: Reference Node and MutationObserver off of the window object rat…

…her than globally (#77)

You have to handle shims yourself if not using jest without this

src/get-node-text.js

@@ -1,7 +1,8 @@
 function getNodeText(node) {
   return Array.from(node.childNodes)
     .filter(
-      child => child.nodeType === Node.TEXT_NODE && Boolean(child.textContent),
+      child =>
+        child.nodeType === window.Node.TEXT_NODE && Boolean(child.textContent),
     )
     .map(c => c.textContent)
     .join(' ')

src/wait-for-element.js

@@ -46,7 +46,7 @@ function waitForElement(
       onDone(lastError || new Error('Timed out in waitForElement.'), null)
     }
     timer = setTimeout(onTimeout, timeout)
-    observer = new MutationObserver(onMutation)
+    observer = new window.MutationObserver(onMutation)
     observer.observe(container, mutationObserverOptions)
     if (callback !== undefined) {
       onMutation()