To serve the site:

bundle exec jekyll serve

To run locally, use this diff in Gemfile

@@ -7,7 +7,8 @@ source "https://rubygems.org"
 #
 # This will help ensure the proper Jekyll version is running.
 # Happy Jekylling!
-gem "jekyll", "~> 3.6.3"
+#gem "jekyll", "~> 3.6.3"
+gem "jekyll", "~> 3.3.0"
 #gem "just-the-docs"#, "~> 2.5"
 # If you want to use GitHub Pages, remove the "gem "jekyll"" above and
 # uncomment the line below. To upgrade, run `bundle update github-pages`.