Make use of "description" property in data array.

Simply make the following changes to radar.js:

After line 58, add:

`description: entry.description,`

After line 221, add:

`.attr('title',function(d) { return d.description })`

And voila, we now have support for the description in the data array.

Previously, it was defined in the test.html example but not used anywhere in the code.
