Restore Gemfile and Gemfile.lock (#2445)

Gemfile

@@ -0,0 +1,9 @@
+source 'https://rubygems.org'
+gem 'jekyll', '3.7.2'
+gem 'tzinfo'
+gem 'tzinfo-data'
+group :jekyll_plugins do
+  gem 'jekyll-feed', '0.9.3'
+  gem 'jekyll-seo-tag', '2.4.0'
+  gem 'jekyll-sitemap', '1.2.0'
+end

Gemfile.lock

@@ -0,0 +1,79 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    addressable (2.5.2)
+      public_suffix (>= 2.0.2, < 4.0)
+    colorator (1.1.0)
+    concurrent-ruby (1.0.5)
+    em-websocket (0.5.1)
+      eventmachine (>= 0.12.9)
+      http_parser.rb (~> 0.6.0)
+    eventmachine (1.2.5)
+    eventmachine (1.2.5-x64-mingw32)
+    ffi (1.9.18)
+    ffi (1.9.18-x64-mingw32)
+    forwardable-extended (2.6.0)
+    http_parser.rb (0.6.0)
+    i18n (0.9.3)
+      concurrent-ruby (~> 1.0)
+    jekyll (3.7.2)
+      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)
+      liquid (~> 4.0)
+      mercenary (~> 0.3.3)
+      pathutil (~> 0.9)
+      rouge (>= 1.7, < 4)
+      safe_yaml (~> 1.0)
+    jekyll-feed (0.9.3)
+      jekyll (~> 3.3)
+    jekyll-sass-converter (1.5.2)
+      sass (~> 3.4)
+    jekyll-seo-tag (2.4.0)
+      jekyll (~> 3.3)
+    jekyll-sitemap (1.2.0)
+      jekyll (~> 3.3)
+    jekyll-watch (2.0.0)
+      listen (~> 3.0)
+    kramdown (1.16.2)
+    liquid (4.0.0)
+    listen (3.1.5)
+      rb-fsevent (~> 0.9, >= 0.9.4)
+      rb-inotify (~> 0.9, >= 0.9.7)
+      ruby_dep (~> 1.2)
+    mercenary (0.3.6)
+    pathutil (0.16.1)
+      forwardable-extended (~> 2.6)
+    public_suffix (3.0.1)
+    rb-fsevent (0.10.2)
+    rb-inotify (0.9.10)
+      ffi (>= 0.5.0, < 2)
+    rouge (3.1.1)
+    ruby_dep (1.5.0)
+    safe_yaml (1.0.4)
+    sass (3.5.5)
+      sass-listen (~> 4.0.0)
+    sass-listen (4.0.0)
+      rb-fsevent (~> 0.9, >= 0.9.4)
+      rb-inotify (~> 0.9, >= 0.9.7)
+    thread_safe (0.3.6)
+    tzinfo (1.2.5)
+      thread_safe (~> 0.1)
+    tzinfo-data (1.2018.3)
+      tzinfo (>= 1.0.0)
+PLATFORMS
+  ruby
+  x64-mingw32
+DEPENDENCIES
+  jekyll (= 3.7.2)
+  jekyll-feed (= 0.9.3)
+  jekyll-seo-tag (= 2.4.0)
+  jekyll-sitemap (= 1.2.0)
+  tzinfo
+  tzinfo-data
+BUNDLED WITH
+   1.16.1