Please add a license!

[RuubixO]

Hi there,

Thank you for a great tutorial and letting us see a great code example. I always prefer to know explicitly how you would want us to use/reuse code that in which you put your own time and work. Let us know how you want us to respect and properly use your work (I know you have a bit on the tutorial page saying we can use this as a base, but more clarification would be very helpful!).

Cheers and keep up the great work!