Log Message:
Update to 2.6.1

Changelog:
2.6.1
Development Fixes
    Test against Jekyll 4.x (#336)

2.6.0
Minor Enhancements
    Twitter Image and Title (#330)

Bug Fixes
    Do not cache the drop payload for SeoTag (#306)
    Update url of schema website (#296)

Development Fixes
    Relax version constraint on Bundler (#325)
    chore(ci): Add Ruby 2.6, drop Ruby 2.3 (#326)
    chore (ci): remove deprecated sudo: false in .travis.yml (#333)
    Lint Ruby code with rubocop-jekyll gem (#302)
    chore(deps): bump rubocop-jekyll to v0.4 (#320)
    chore(deps): bump rubocop-jekyll to v0.3 (#316)
    Correct RuboCop offenses in spec files (#319)

Documentation
    Rectify error in Usage documentation (#328)