Update Jekyll to v4.0.0.

.gitignore

@@ -6,3 +6,4 @@
 /node_modules
 /npm-debug.log
 /source/.jekyll-metadata
+/source/.jekyll-cache

Gemfile

@@ -1,6 +1,6 @@
 source 'https://rubygems.org'
 
-gem 'jekyll', '~> 3.8.6'
+gem 'jekyll', '~> 4.0.0'
 gem 'jekyll-avatar', '~> 0.7.0'
 gem 'jekyll-email-protect', '~> 1.0.3'
 gem 'jekyll-feed', '~> 0.13.0'

Gemfile.lock

@@ -14,34 +14,38 @@ GEM
     ffi (1.11.2-x64-mingw32)
     forwardable-extended (2.6.0)
     http_parser.rb (0.6.0)
-    i18n (0.9.5)
+    i18n (1.7.0)
       concurrent-ruby (~> 1.0)
-    jekyll (3.8.6)
+    jekyll (4.0.0)
       addressable (~> 2.4)
       colorator (~> 1.0)
       em-websocket (~> 0.5)
-      i18n (~> 0.7)
-      jekyll-sass-converter (~> 1.0)
+      i18n (>= 0.9.5, < 2)
+      jekyll-sass-converter (~> 2.0)
       jekyll-watch (~> 2.0)
-      kramdown (~> 1.14)
+      kramdown (~> 2.1)
+      kramdown-parser-gfm (~> 1.0)
       liquid (~> 4.0)
       mercenary (~> 0.3.3)
       pathutil (~> 0.9)
-      rouge (>= 1.7, < 4)
+      rouge (~> 3.0)
       safe_yaml (~> 1.0)
+      terminal-table (~> 1.8)
     jekyll-avatar (0.7.0)
       jekyll (>= 3.0, < 5.0)
     jekyll-email-protect (1.0.3)
     jekyll-feed (0.13.0)
       jekyll (>= 3.7, < 5.0)
     jekyll-paginate (1.1.0)
-    jekyll-sass-converter (1.5.2)
-      sass (~> 3.4)
+    jekyll-sass-converter (2.0.1)
+      sassc (> 2.0.1, < 3.0)
     jekyll-sitemap (1.3.1)
       jekyll (>= 3.7, < 5.0)
     jekyll-watch (2.2.1)
       listen (~> 3.0)
-    kramdown (1.17.0)
+    kramdown (2.1.0)
+    kramdown-parser-gfm (1.1.0)
+      kramdown (~> 2.0)
     liquid (4.0.3)
     listen (3.2.0)
       rb-fsevent (~> 0.10, >= 0.10.3)
@@ -55,19 +59,21 @@ GEM
       ffi (~> 1.0)
     rouge (3.13.0)
     safe_yaml (1.0.5)
-    sass (3.7.4)
-      sass-listen (~> 4.0.0)
-    sass-listen (4.0.0)
-      rb-fsevent (~> 0.9, >= 0.9.4)
-      rb-inotify (~> 0.9, >= 0.9.7)
+    sassc (2.2.1)
+      ffi (~> 1.9)
+    sassc (2.2.1-x64-mingw32)
+      ffi (~> 1.9)
+    terminal-table (1.8.0)
+      unicode-display_width (~> 1.1, >= 1.1.1)
+    unicode-display_width (1.6.0)
     wdm (0.1.1)
 
 PLATFORMS
   ruby
   x64-mingw32
 
 DEPENDENCIES
-  jekyll (~> 3.8.6)
+  jekyll (~> 4.0.0)
   jekyll-avatar (~> 0.7.0)
   jekyll-email-protect (~> 1.0.3)
   jekyll-feed (~> 0.13.0)