Update devDependencies and gems.

Downgrade bundlesize until they make brotli optional since it doesn't work with node.js 10.x yet.

So, babel, qunit/karma-qunit and bundle-size aren't the latest versions.

Gemfile.lock

@@ -8,15 +8,15 @@ GEM
     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)
+    eventmachine (1.2.6)
+    eventmachine (1.2.6-x64-mingw32)
     ffi (1.9.23)
     ffi (1.9.23-x64-mingw32)
     forwardable-extended (2.6.0)
     http_parser.rb (0.6.0)
     i18n (0.9.5)
       concurrent-ruby (~> 1.0)
-    jekyll (3.8.0)
+    jekyll (3.8.1)
       addressable (~> 2.4)
       colorator (~> 1.0)
       em-websocket (~> 0.5)
@@ -35,8 +35,8 @@ GEM
       sass (~> 3.4)
     jekyll-sitemap (1.2.0)
       jekyll (~> 3.3)
-    jekyll-toc (0.5.2)
-      nokogiri (~> 1.6)
+    jekyll-toc (0.6.0)
+      nokogiri (~> 1.7)
     jekyll-watch (2.0.0)
       listen (~> 3.0)
     kramdown (1.16.2)
@@ -71,10 +71,10 @@ PLATFORMS
   x64-mingw32
 
 DEPENDENCIES
-  jekyll (~> 3.8.0)
+  jekyll (~> 3.8.1)
   jekyll-redirect-from (~> 0.13.0)
   jekyll-sitemap (~> 1.2.0)
-  jekyll-toc (~> 0.5.1)
+  jekyll-toc (~> 0.6.0)
 
 BUNDLED WITH
    1.16.1