Bump kramdown from 1.17.0 to 2.3.1

Bumps [kramdown](https://github.com/gettalong/kramdown) from 1.17.0 to 2.3.1.
- [Release notes](https://github.com/gettalong/kramdown/releases)
- [Changelog](https://github.com/gettalong/kramdown/blob/master/doc/news.page)
- [Commits](https://github.com/gettalong/kramdown/commits)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Gemfile.lock

@@ -41,16 +41,16 @@ GEM
     builder (3.2.3)
     color (1.8)
     colorator (1.1.0)
-    concurrent-ruby (1.1.5)
+    concurrent-ruby (1.1.8)
     crass (1.0.4)
-    em-websocket (0.5.1)
+    em-websocket (0.5.2)
       eventmachine (>= 0.12.9)
       http_parser.rb (~> 0.6.0)
     erubis (2.7.0)
     eventmachine (1.2.7)
     faraday (0.15.3)
       multipart-post (>= 1.2, < 3)
-    ffi (1.9.25)
+    ffi (1.15.0)
     forwardable-extended (2.6.0)
     geo_pattern (1.2.1)
       color (~> 1.5)
@@ -59,14 +59,14 @@ GEM
     http_parser.rb (0.6.0)
     i18n (0.9.5)
       concurrent-ruby (~> 1.0)
-    jekyll (3.8.4)
+    jekyll (3.9.0)
       addressable (~> 2.4)
       colorator (~> 1.0)
       em-websocket (~> 0.5)
       i18n (~> 0.7)
       jekyll-sass-converter (~> 1.0)
       jekyll-watch (~> 2.0)
-      kramdown (~> 1.14)
+      kramdown (>= 1.17, < 3)
       liquid (~> 4.0)
       mercenary (~> 0.3.3)
       pathutil (~> 0.9)
@@ -83,14 +83,14 @@ GEM
       sass (~> 3.4)
     jekyll-sitemap (1.3.1)
       jekyll (>= 3.7, < 5.0)
-    jekyll-watch (2.1.2)
+    jekyll-watch (2.2.1)
       listen (~> 3.0)
-    kramdown (1.17.0)
-    liquid (4.0.1)
-    listen (3.1.5)
-      rb-fsevent (~> 0.9, >= 0.9.4)
-      rb-inotify (~> 0.9, >= 0.9.7)
-      ruby_dep (~> 1.2)
+    kramdown (2.3.1)
+      rexml
+    liquid (4.0.3)
+    listen (3.5.0)
+      rb-fsevent (~> 0.10, >= 0.10.3)
+      rb-inotify (~> 0.9, >= 0.9.10)
     loofah (2.2.3)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
@@ -106,14 +106,14 @@ GEM
       mini_portile2 (~> 2.3.0)
     octokit (4.13.0)
       sawyer (~> 0.8.0, >= 0.5.3)
-    pathutil (0.16.1)
+    pathutil (0.16.2)
       forwardable-extended (~> 2.6)
     protobuf (3.8.4)
       activesupport (>= 3.2)
       middleware
       thor
       thread_safe
-    public_suffix (3.0.3)
+    public_suffix (3.1.1)
     rack (1.6.10)
     rack-test (0.6.3)
       rack (>= 1.0)
@@ -142,16 +142,16 @@ GEM
       rake (>= 0.8.7)
       thor (>= 0.18.1, < 2.0)
     rake (12.3.2)
-    rb-fsevent (0.10.3)
-    rb-inotify (0.9.10)
-      ffi (>= 0.5.0, < 2)
-    rouge (3.4.1)
+    rb-fsevent (0.10.4)
+    rb-inotify (0.10.1)
+      ffi (~> 1.0)
+    rexml (3.2.4)
+    rouge (3.26.0)
     rough (0.2.6)
       protobuf (>= 3.4)
       rails (~> 4.1)
-    ruby_dep (1.5.0)
-    safe_yaml (1.0.4)
-    sass (3.6.0)
+    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)