Merge pull request #299 from fastai/dependabot/bundler/docs_src/kramdown-2.3.1

Bump kramdown from 2.3.0 to 2.3.1 in /docs_src

Author: jph00

docs_src/Gemfile.lock

@@ -33,7 +33,7 @@ GEM
       sassc (> 2.0.1, < 3.0)
     jekyll-watch (2.2.1)
       listen (~> 3.0)
-    kramdown (2.3.0)
+    kramdown (2.3.1)
       rexml
     kramdown-parser-gfm (1.1.0)
       kramdown (~> 2.0)