Should we check randomness of custom Random?

Hello,

It could be nice to check the Randomness of modified function. I am looking at you `NextFloat()` and `NextLong()`. I may to be sure that our modification keep an uniform distribution.

To check this we can implement a Test case with Chi-Square.

See :
- [Verify distribution uniformity/Chi-squared test - Rosetta Code](http://rosettacode.org/wiki/Verify_distribution_uniformity/Chi-squared_test#C)

Gamma :
- [Gamma function - Rosetta Code](http://rosettacode.org/wiki/Gamma_function#Java)
- [Special Function(s) for C# - CodeProject](http://www.codeproject.com/Articles/11647/Special-Function-s-for-C)

I started my own [implementation](https://gist.github.com/aloisdg/9a94b070d0caa5a32d80).