Merge pull request #47 from fastai/dependabot/bundler/docs/kramdown-2.3.1

Bump kramdown from 2.3.0 to 2.3.1 in /docs

Author: Hamel Husain

docs/Gemfile.lock

@@ -36,7 +36,7 @@ GEM
       jekyll-seo-tag (~> 2.0)
     jekyll-watch (2.2.1)
       listen (~> 3.0)
-    kramdown (2.3.0)
+    kramdown (2.3.1)
       rexml
     liquid (4.0.3)
     listen (3.3.1)