Implementation of Josephus Problem (#36)

- This is a naive solution that uses "killer iterator" approach - this
  iterator kills elements by step of K, so when number of elements
becomes less than K, these elements are survivors. More efficient
implementation of this algorithm can exist - some math reasoning which
yields direct math formula, but implementation of this will be another story.
Update README with Josephus Problem
Merge pull request #68 from stanislaw/master

Implementation of Josephus Problem (#36)