mir.stat: statistical functions

[wilzbach]

Yesterday I realized that mir.random heavily depends on mir.stat as it needs statistical tests to verify its random algorithsm.
Well here is the WIP part for this - it includes already includes an online variance + mean report, moreover I plan to add one or two statistical tests in the first version. What else do you want to see in the initial version of mir.stat (#49)?

TODO:

• more precision tests

[codecov-io]

Current coverage is 98.16%

Merging #90 into master will increase coverage by +0.04% as of b2c33f4

@@            master     #90   diff @@
======================================
  Files            7       8     +1
  Stmts         2500    2559    +59
  Branches         0       0       
  Methods          0       0       
======================================
+ Hit           2453    2512    +59
  Partial          0       0       
  Missed          47      47       

Review entire Coverage Diff as of b2c33f4

Powered by Codecov. Updated on successful CI builds.

[9il]

Don't spend time on this.

The better option for testing RNGs is a collection of PDF functions, drawing tool, and log-likelihood. Plus articles!!!

[9il]

And do not work on best API. It would be reworked, maybe few times