add almost sorted input and fix use of private stdlib-function

I talked to you after todays meeting about the illegal use of std::__insertion_sort in the wikisort-implementation. This patch fixes this by using the insertion-sort from [here](http://en.cppreference.com/w/cpp/algorithm/rotate).

The other thing that this does is adding the possibility to start with an almost sorted range, which might be useful for algorithms like smoothsort and timsort.