Update devDependencies and gems.

Also, add wdm gem for Windows since it's recommended.

Gemfile

@@ -1,8 +1,9 @@
 source 'https://rubygems.org'
 
-gem 'jekyll', '~> 3.8.4'
+gem 'jekyll', '~> 3.8.5'
 gem 'jekyll-avatar', '~> 0.6.0'
 gem 'jekyll-email-protect', '~> 1.0.3'
 gem 'jekyll-feed', '~> 0.11.0'
 gem 'jekyll-paginate', '~> 1.1.0'
 gem 'jekyll-sitemap', '~> 1.2.0'
+gem 'wdm', '~> 0.1.1', :install_if => Gem.win_platform?

Gemfile.lock

@@ -4,7 +4,7 @@ GEM
     addressable (2.5.2)
       public_suffix (>= 2.0.2, < 4.0)
     colorator (1.1.0)
-    concurrent-ruby (1.0.5)
+    concurrent-ruby (1.1.3)
     em-websocket (0.5.1)
       eventmachine (>= 0.12.9)
       http_parser.rb (~> 0.6.0)
@@ -16,7 +16,7 @@ GEM
     http_parser.rb (0.6.0)
     i18n (0.9.5)
       concurrent-ruby (~> 1.0)
-    jekyll (3.8.4)
+    jekyll (3.8.5)
       addressable (~> 2.4)
       colorator (~> 1.0)
       em-websocket (~> 0.5)
@@ -39,7 +39,7 @@ GEM
       sass (~> 3.4)
     jekyll-sitemap (1.2.0)
       jekyll (~> 3.3)
-    jekyll-watch (2.1.1)
+    jekyll-watch (2.1.2)
       listen (~> 3.0)
     kramdown (1.17.0)
     liquid (4.0.1)
@@ -48,7 +48,7 @@ GEM
       rb-inotify (~> 0.9, >= 0.9.7)
       ruby_dep (~> 1.2)
     mercenary (0.3.6)
-    pathutil (0.16.1)
+    pathutil (0.16.2)
       forwardable-extended (~> 2.6)
     public_suffix (3.0.3)
     rb-fsevent (0.10.3)
@@ -57,23 +57,25 @@ GEM
     rouge (3.3.0)
     ruby_dep (1.5.0)
     safe_yaml (1.0.4)
-    sass (3.6.0)
+    sass (3.7.2)
       sass-listen (~> 4.0.0)
     sass-listen (4.0.0)
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
+    wdm (0.1.1)
 
 PLATFORMS
   ruby
   x64-mingw32
 
 DEPENDENCIES
-  jekyll (~> 3.8.4)
+  jekyll (~> 3.8.5)
   jekyll-avatar (~> 0.6.0)
   jekyll-email-protect (~> 1.0.3)
   jekyll-feed (~> 0.11.0)
   jekyll-paginate (~> 1.1.0)
   jekyll-sitemap (~> 1.2.0)
+  wdm (~> 0.1.1)
 
 BUNDLED WITH
-   1.16.6
+   1.17.1