Implement the Westfall-Young Multiple Testing Correction

[s3alfisc]

Context

The main competitor to the Romano-Wolf multiple testing correction appears to be the method by Wesfall & Young.

To Do

• Implement the stepwise procedure by WF as described in the appendix of the rwolf paper.
• Add a wyoung() function that mimics rwolf().
• Implement unit tests against Stata's wyoung package (if possible, it will likely be vary slow if run with many iterations).