diff-lcs 1.3

Diff::LCS computes the difference between two Enumerable sequences using the McIlroy-Hunt longest common subsequence (LCS) algorithm. It includes utilities to create a simple HTML diff output format and a standard diff-like tool. This is release 1.3, providing a tentative fix to a long-standing issue related to incorrect detection of a patch direction. Also modernizes the gem infrastructure, testing infrastructure, and provides a warning-free experience to Ruby 2.4 users.