Re: Nimgame 2

[Vladar]

May the [4th alpha](https://vladar4.github.io/nimgame2/index.html) of Nimgame 2 
be with you!

* * *

**New stuff:**

  * GUI:
    * RadioGroup
    * RadioButton
  * IndexedImage
  * PerspectiveImage
  * TextureAtlas
  * joysticks support
  * window management procedures
  * 4 new demos
  * [first tutorial](https://vladar4.github.io/nimgame2/tut101_bounce.html)