upgrade jekyll

Gemfile

@@ -1,9 +1,9 @@
 source 'https://rubygems.org'
 
-gem 'jekyll', '3.8.5'
+gem 'jekyll', '4.1.1'
 
 group :jekyll_plugins do
-  gem 'jekyll-feed', '0.11.0'
+  gem 'jekyll-feed', '0.15.0'
-  gem 'jekyll-seo-tag', '2.6.0'
+  gem 'jekyll-seo-tag', '2.6.1'
-  gem 'jekyll-sitemap', '1.2.0'
+  gem 'jekyll-sitemap', '1.4.0'
 end

Gemfile.lock

@@ -1,72 +1,76 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    addressable (2.6.0)
+    addressable (2.7.0)
-      public_suffix (>= 2.0.2, < 4.0)
+      public_suffix (>= 2.0.2, < 5.0)
     colorator (1.1.0)
-    concurrent-ruby (1.1.5)
+    concurrent-ruby (1.1.7)
-    em-websocket (0.5.1)
+    em-websocket (0.5.2)
       eventmachine (>= 0.12.9)
       http_parser.rb (~> 0.6.0)
     eventmachine (1.2.7)
-    ffi (1.10.0)
+    ffi (1.13.1)
     forwardable-extended (2.6.0)
     http_parser.rb (0.6.0)
-    i18n (0.9.5)
+    i18n (1.8.5)
       concurrent-ruby (~> 1.0)
-    jekyll (3.8.5)
+    jekyll (4.1.1)
       addressable (~> 2.4)
       colorator (~> 1.0)
       em-websocket (~> 0.5)
-      i18n (~> 0.7)
+      i18n (~> 1.0)
-      jekyll-sass-converter (~> 1.0)
+      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)
+      mercenary (~> 0.4.0)
       pathutil (~> 0.9)
-      rouge (>= 1.7, < 4)
+      rouge (~> 3.0)
       safe_yaml (~> 1.0)
-    jekyll-feed (0.11.0)
+      terminal-table (~> 1.8)
-      jekyll (~> 3.3)
+    jekyll-feed (0.15.0)
-    jekyll-sass-converter (1.5.2)
+      jekyll (>= 3.7, < 5.0)
-      sass (~> 3.4)
+    jekyll-sass-converter (2.1.0)
-    jekyll-seo-tag (2.6.0)
+      sassc (> 2.0.1, < 3.0)
-      jekyll (~> 3.3)
+    jekyll-seo-tag (2.6.1)
-    jekyll-sitemap (1.2.0)
+      jekyll (>= 3.3, < 5.0)
-      jekyll (~> 3.3)
+    jekyll-sitemap (1.4.0)
+      jekyll (>= 3.7, < 5.0)
     jekyll-watch (2.2.1)
       listen (~> 3.0)
-    kramdown (1.17.0)
+    kramdown (2.3.0)
+      rexml
+    kramdown-parser-gfm (1.1.0)
+      kramdown (~> 2.0)
     liquid (4.0.3)
-    listen (3.1.5)
+    listen (3.2.1)
-      rb-fsevent (~> 0.9, >= 0.9.4)
+      rb-fsevent (~> 0.10, >= 0.10.3)
-      rb-inotify (~> 0.9, >= 0.9.7)
+      rb-inotify (~> 0.9, >= 0.9.10)
-      ruby_dep (~> 1.2)
+    mercenary (0.4.0)
-    mercenary (0.3.6)
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
-    public_suffix (3.0.3)
+    public_suffix (4.0.6)
-    rb-fsevent (0.10.3)
+    rb-fsevent (0.10.4)
-    rb-inotify (0.10.0)
+    rb-inotify (0.10.1)
       ffi (~> 1.0)
-    rouge (3.3.0)
+    rexml (3.2.4)
-    ruby_dep (1.5.0)
+    rouge (3.23.0)
     safe_yaml (1.0.5)
-    sass (3.7.4)
+    sassc (2.4.0)
-      sass-listen (~> 4.0.0)
+      ffi (~> 1.9)
-    sass-listen (4.0.0)
+    terminal-table (1.8.0)
-      rb-fsevent (~> 0.9, >= 0.9.4)
+      unicode-display_width (~> 1.1, >= 1.1.1)
-      rb-inotify (~> 0.9, >= 0.9.7)
+    unicode-display_width (1.7.0)
 
 PLATFORMS
   ruby
 
 DEPENDENCIES
-  jekyll (= 3.8.5)
+  jekyll (= 4.1.1)
-  jekyll-feed (= 0.11.0)
+  jekyll-feed (= 0.15.0)
-  jekyll-seo-tag (= 2.6.0)
+  jekyll-seo-tag (= 2.6.1)
-  jekyll-sitemap (= 1.2.0)
+  jekyll-sitemap (= 1.4.0)
 
 BUNDLED WITH
-   2.0.1
+   2.1.4