Update Nokogiri documentation (1.9.0)

Author: Thibaut

lib/docs/scrapers/nokogiri2.rb

@@ -1,17 +1,22 @@
 module Docs
   class Nokogiri2 < Rdoc
+    # Instructions:
+    #   1. Download the latest release at https://github.com/sparklemotion/nokogiri/releases
+    #   2. Run "bundle install && bundle exec rake docs" (in the Nokogiri directory)
+    #   4. Copy the "doc" directory to "docs/nokgiri"
+
     self.name = 'Nokogiri'
     self.slug = 'nokogiri'
-    self.release = '1.8.1'
+    self.release = '1.9.0'
 
     html_filters.replace 'rdoc/entries', 'nokogiri2/entries'
 
     options[:root_title] = 'Nokogiri'
     options[:only_patterns] = [/\ANokogiri/, /\AXSD/]
 
     options[:attribution] = <<-HTML
-      &copy; 2008&ndash;2017 Aaron Patterson, Mike Dalessio, Charles Nutter, Sergio Arbeo<br>
-      Patrick Mahoney, Yoko Harada, Akinori Musha, John Shahid<br>
+      &copy; 2008&ndash;2018 Aaron Patterson, Mike Dalessio, Charles Nutter, Sergio Arbeo,<br>
+      Patrick Mahoney, Yoko Harada, Akinori Musha, John Shahid, Lars Kanis<br>
       Licensed under the MIT License.
     HTML
   end