Update Yarn documentation (0.19.1)

assets/javascripts/templates/pages/about_tmpl.coffee

@@ -596,7 +596,7 @@ credits = [
     'https://raw.githubusercontent.com/webpack/webpack/master/LICENSE'
   ], [
     'Yarn',
-    '2016 Yarn Contributors',
+    '2016-2017 Yarn Contributors',
     'BSD',
     'https://raw.githubusercontent.com/yarnpkg/yarn/master/LICENSE'
   ], [

lib/docs/scrapers/yarn.rb

@@ -1,7 +1,7 @@
 module Docs
   class Yarn < UrlScraper
     self.type = 'yarn'
-    self.release = '0.18.1'
+    self.release = '0.19.1'
     self.base_url = 'https://yarnpkg.com/en/docs/'
     self.links = {
       home: 'https://yarnpkg.com/',
@@ -17,7 +17,7 @@ module Docs
     options[:skip_patterns] = [/\Aorg\//]
 
     options[:attribution] = <<-HTML
-      &copy; 2016 Yarn Contributors<br>
+      &copy; 2016&ndash;2017 Yarn Contributors<br>
       Licensed under the BSD License.
     HTML
   end