Updates based on @mikes-caplin's feedback

Updates based on @mikes-caplin's feedback.

I've created a new issue for the point around appending the Blades to the UI as #12.

The main big change is to add support for code highlighting, used when highlighting changes in the code.

I went for the simple approach of using valid JavaScript or HTML comments that are then replace by some JavaScript.

e.g.

```javascript
var anOldVar = "something"'
/*** new code ***/
var aNewVar = "something else";
/*** end of new code ***/
```

and

```html
<div>An old element</div>
<!-- new code -->
<div>A new element</div>
<!-- end of new code -->
```

This means that it's human readable even if the JavaScript doesn't work.

It results in something like the following:

![screen shot 2013-11-08 at 18 01 51](https://f.cloud.github.com/assets/328367/1502787/3c9c007c-48a0-11e3-942f-947de7802150.png)