[d3-state-visualizer] Tooltip on chart view does not handle HTML entities correctly

[zalmoxisus]

To reproduce:

• Dispatch an action that results in some state like book.title where title has a value of cars & trucks
• Open the Redux devtool
• Go to the chart view
• Navigate the state chart from book to title
• Hover over title so you can see its value

The tooltip incorrectly renders HTML contained within the state value. For example, you'd see something like cars & trucks when you should see cars & trucks.

If you click on title to see the table view then the HTML is rendered as expected.

Moved from https://github.com/zalmoxisus/redux-devtools-extension/issues/462

UPDATE: This is from d3-state-visualizer, not d3tooltip. We'll get it merged here later.