Add tests for DustJS to JSPerf

[JamesMGreene]

Performance benchmarks are a huge factor for many devs when choosing a templating library. There is an existing JSPerf entry with most all of the templating libraries in it already but I don't see DustJS present. Would you mind adding it?

Here is the latest revision:
http://jsperf.com/dom-vs-innerhtml-based-templating/402