Switch the Virtual DOM CodePen to the Vue account

[skirtles-code]

Closes #451.

In addition to migrating the CodePen to the Vue account, I have made the following changes to the Haml. Emphasis mine:

Line 9:

The virtual DOM in is a lightweight JavaScript object, created by this render function

The virtual DOM is a lightweight JavaScript object, created by this render function

Line 15:

If we need to update the list items, we do so in javascript

If we need to update the list items, we do so in JavaScript

Line 17:

The Virtual DOM allows us to make performant update our UIs!

The Virtual DOM allows us to make performant updates to our UIs!

Line 92:

= succeed "," do

= succeed ", [" do