update jekyll/nokogiri for compatibility with ruby 2.7

Gemfile

@@ -7,7 +7,9 @@ source "https://rubygems.org"
 #
 # This will help ensure the proper Jekyll version is running.
 # Happy Jekylling!
-gem "jekyll", "~> 4.0.0"
+# gem "jekyll", "~> 4.0.0"
+gem "nokogiri", ">= 1.11.0.rc1"
+gem "jekyll", github: "jekyll/jekyll"
 gem "html-proofer"
 # This is the default theme for new Jekyll sites. You may change this to anything you like.
 # gem "minima", "~> 2.5"

Gemfile.lock

@@ -1,3 +1,23 @@
+GIT
+  remote: https://github.com/jekyll/jekyll.git
+  revision: ab6ef0b257e4c7aafec0518d93bea3e9c4b75b75
+  specs:
+    jekyll (4.0.0)
+      addressable (~> 2.4)
+      colorator (~> 1.0)
+      em-websocket (~> 0.5)
+      i18n (>= 0.9.5, < 2)
+      jekyll-sass-converter (~> 2.0)
+      jekyll-watch (~> 2.0)
+      kramdown (~> 2.1)
+      kramdown-parser-gfm (~> 1.0)
+      liquid (~> 4.0)
+      mercenary (~> 0.4.0)
+      pathutil (~> 0.9)
+      rouge (~> 3.0)
+      safe_yaml (~> 1.0)
+      terminal-table (~> 1.8)
+
 GEM
   remote: https://rubygems.org/
   specs:
@@ -24,21 +44,6 @@ GEM
     http_parser.rb (0.6.0)
     i18n (1.8.2)
       concurrent-ruby (~> 1.0)
-    jekyll (4.0.0)
-      addressable (~> 2.4)
-      colorator (~> 1.0)
-      em-websocket (~> 0.5)
-      i18n (>= 0.9.5, < 2)
-      jekyll-sass-converter (~> 2.0)
-      jekyll-watch (~> 2.0)
-      kramdown (~> 2.1)
-      kramdown-parser-gfm (~> 1.0)
-      liquid (~> 4.0)
-      mercenary (~> 0.3.3)
-      pathutil (~> 0.9)
-      rouge (~> 3.0)
-      safe_yaml (~> 1.0)
-      terminal-table (~> 1.8)
     jekyll-sass-converter (2.1.0)
       sassc (> 2.0.1, < 3.0)
     jekyll-watch (2.2.1)
@@ -50,9 +55,9 @@ GEM
     listen (3.2.1)
       rb-fsevent (~> 0.10, >= 0.10.3)
       rb-inotify (~> 0.9, >= 0.9.10)
-    mercenary (0.3.6)
+    mercenary (0.4.0)
     mini_portile2 (2.4.0)
-    nokogiri (1.10.9)
+    nokogiri (1.11.0.rc1)
       mini_portile2 (~> 2.4.0)
     nokogumbo (2.0.2)
       nokogiri (~> 1.8, >= 1.8.4)
@@ -86,7 +91,8 @@ PLATFORMS
 
 DEPENDENCIES
   html-proofer
-  jekyll (~> 4.0.0)
+  jekyll!
+  nokogiri (>= 1.11.0.rc1)
   tzinfo (~> 1.2)
   tzinfo-data
   wdm (~> 0.1.1)