Log Message:
Update ruby-diff-lcs to 1.3.

## 1.3 / 2017-01-18

*   Bugs fixed:

    *   Fixed an error for bin/ldiff --version. Fixes [issue #21][].
    *   Force Diff::LCS::Change and Diff::LCS::ContextChange to only perform
        equality comparisons against themselves. Provided by Kevin Mook in
        [pull request #29][].
    *   Fix tab expansion in htmldiff, provided by Mark Friedgan in
        [pull request #25][].
    *   Silence Ruby 2.4 Fixnum deprecation warnings. Fixxues [issue #38][] and
        [pull request#36][].
    *   Ensure that test dependencies are loaded properly. Fixes [issue #33][]
        and [pull request #34][].
    *   Fix [issue #1][] with incorrect intuition of patch direction. Tentative
        fix, but the previous failure cases pass now.

*   Tooling changes:

    *   Added SimpleCov and Coveralls support.
    *   Change the homepage (temporarily) to the GitHub repo.
    *   Updated testing and gem infrastructure.
    *   Modernized the specs.

*   Cleaned up documentation.

*   Added a Code of Conduct.