www/ruby-jekyll-seo-tag: update to 2.5.0

## 2.5.0 / 2018-05-18

  * Docs: Prevent GitHub Pages from processing Liquid raw tag (#276)

### Documentation

  * Use gems config key for Jekyll < 3.5.0 (#255)
  * docs/usage - replace "below" with correct link (#280)

### Development Fixes

  * Test against Ruby 2.5 (#260)
  * add tests for twitter.card types (#289)
  * Target Ruby 2.3 and Rubocop 0.56.0 (#292)

### Minor Enhancements

  * Add webmaster_verifications for baidu (#263)
  * Include page number in title (#250)
  * Configure default Twitter summary card type (V2) (#225)

(taca)