Change find_end:
1.Fix for ForwardIterator when [first2, last2) is empty.
2.Fix RandomAccessIterator version.(search from last1)
3.Add BidirectionalIterator version.(search from last1)
4.Add sprout::detail::search_one_rev helper function for
  BidirectionalIterator version.
Merge pull request #27 from kariya-mitsuru/find_end

[algorithm.find_end] Change find_end