Simplest possible sort impl

This ist the simplest possible sort implementation I found (the one in libc++ is too optimized). 
It allows to at least try the sort interface.

Test using default comparison are provided.

TODO:
- test using iterators, custom comparisons, and projections.
- test file needs cleaning.
Take a sentinel here and then use `next_to(begin, end) to find the real end before starting. I'm now of the opinion that all the algorithms should work with `Iterables`. `sort` is generally O(N log N). An O(N) probe for the end doesn't change that.