Require nokogiri 1.8.2 or greater

Addresses CVE-2017-18258
https://nvd.nist.gov/vuln/detail/CVE-2017-18258

github-pages.gemspec

@@ -26,7 +26,7 @@ Gem::Specification.new do |s|
 
   s.add_dependency("mercenary", "~> 0.3")
   s.add_dependency("terminal-table", "~> 1.4")
-  s.add_dependency("nokogiri", ">= 1.8.1", "< 2.0") # CVE-2017-9050
+  s.add_dependency("nokogiri", ">= 1.8.2", "< 2.0") # CVE-2017-9050, CVE-2017-18258
   s.add_development_dependency("rspec", "~> 3.3")
   s.add_development_dependency("rainbow", "~> 2.1.0")
   s.add_development_dependency("pry", "~> 0.10")