Merge pull request #561 from github/github-pages-health-check-v1-8-1

Bump github-pages-health-check to v1.8.1

lib/github-pages/dependencies.rb

@@ -17,7 +17,7 @@ module GitHubPages
       # Misc
       "liquid"                    => "4.0.0",
       "rouge"                     => "2.2.1",
-      "github-pages-health-check" => "1.7.4",
+      "github-pages-health-check" => "1.8.1",
 
       # Plugins
       "jekyll-redirect-from"   => "0.13.0",