Added webrick gem to make the development docker container work

src/Gemfile

@@ -19,6 +19,10 @@ group :jekyll_plugins do
   gem "jekyll-coffeescript"
 end
 
+group :development do
+  gem "webrick"
+end
+
 # Windows and JRuby does not include zoneinfo files, so bundle the tzinfo-data gem
 # and associated library.
 platforms :mingw, :x64_mingw, :mswin, :jruby do
@@ -28,4 +32,3 @@ end
 
 # Performance-booster for watching directories on Windows
 gem "wdm", "~> 0.1.1", :platforms => [:mingw, :x64_mingw, :mswin]
-

src/Gemfile.lock

@@ -72,6 +72,7 @@ GEM
     terminal-table (2.0.0)
       unicode-display_width (~> 1.1, >= 1.1.1)
     unicode-display_width (1.7.0)
+    webrick (1.8.1)
 
 PLATFORMS
   ruby
@@ -84,6 +85,7 @@ DEPENDENCIES
   tzinfo (~> 1.2)
   tzinfo-data
   wdm (~> 0.1.1)
+  webrick
 
 BUNDLED WITH
    2.2.24