Added new bsd licence

Hello, we had discussed this by email in late May. 

"Hi Gilles,

Feel free to use the software for your game. Consider it under the
new-BSD licence. I'll update the repo with this when I have time.

I'd love to see what you do with it, so keep me updated!"

I had stopped working on my project for a few weeks so I never got around to integrate dungeon code but now I am preparing too. 

I added the licence like we had discussed.