Fix for handleDomNodeRemoved not being called when parent containers removed from DOM

[Phoebe-G]

WYSIHTML editors created on textareas inside jconfirm dialog boxes were not being properly destroyed when the dialog is closed.

The scenario can be recreated quite easily in the simple example (http://voog.github.io/wysihtml/examples/simple.html) by deleting the form element rather than its child elements.

Browser stacktrace after destroying the dialog/container was:

wysihtml.js:10009 Uncaught TypeError: Cannot read property 'document' of null
getDocument @ wysihtml.js:10009
wysihtml.Editor.wysihtml.lang.Dispatcher.extend.parse @ wysihtml.js:16047
wysihtml.views.Textarea.wysihtml.views.View.extend.setValue @ wysihtml.js:15793
wysihtml.views.Synchronizer.Base.extend.fromComposerToTextarea @ wysihtml.js:15638
(anonymous function) @ wysihtml.js:15678