Add myself to CONTRIBUTORS.md under NICTA.

This seems to be a record of what CLAs people contributed code under.  So I guess I should stay in the AGI and Individual categories as well?

Also, it would be great if someone could update this page when you get a chance:
http://cesiumjs.org/contributors.html

It could say "NICTA (formerly AGI)" or just NICTA, up to you.

I was in a meeting yesterday where someone (outside NICTA) pointed out that this hadn't been updated yet.