Disable gems in _config.yml and enable with bundler instead

- Add `repository` to `_config.yml` as part of GitHub metadata

Gemfile

@@ -1,5 +1,23 @@
 source "https://rubygems.org"
 
-gem "github-pages"
-# gem "jekyll-archives"
-gem "wdm", "~> 0.1.0" if Gem.win_platform?
+# Hello! This is where you manage which Jekyll version is used to run.
+# When you want to use a different version, change it below, save the
+# file and run `bundle install`. Run Jekyll with `bundle exec`, like so:
+#
+#     bundle exec jekyll serve
+#
+# This will help ensure the proper Jekyll version is running.
+# Happy Jekylling!
+
+gem "github-pages", group: :jekyll_plugins
+
+# If you want to use Jekyll native, remove the "gem "github-pages"" line
+# and uncomment the line below. To upgrade, run `bundle update`.
+# gem "jekyll"
+
+gem "wdm", "~> 0.1.0" if Gem.win_platform?
+
+# If you have any plugins, put them here!
+group :jekyll_plugins do
+  # gem "jekyll-archives"
+end