updated jekyll + removed plugin webrick which was apparently not used…

… and caused pbs

Gemfile

@@ -1,10 +1,10 @@
 source "https://rubygems.org"
 
-gem "jekyll", ">= 3.8.5"
-gem "webrick"
+gem "jekyll",  "~> 4.3.4"
+gem "minima", "~> 2.5"
 
 group :jekyll_plugins do
-  gem "jekyll-feed", "~> 0.6"
+  gem "jekyll-feed", "~> 0.12"
   gem "jekyll-paginate", "~> 1.1.0"
   gem "jemoji"
   gem "jekyll-sitemap"
@@ -14,8 +14,13 @@ group :jekyll_plugins do
   gem "jekyll-toc"
 end
 
-# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
-gem "tzinfo-data", platforms: [:mingw, :mswin, :x64_mingw, :jruby]
+# Windows and JRuby does not include zoneinfo files, so bundle the tzinfo-data gem
+# and associated library.
+platforms :mingw, :x64_mingw, :mswin, :jruby do
+  gem "tzinfo", ">= 1", "< 3"
+  gem "tzinfo-data"
+end
 
 # Performance-booster for watching directories on Windows
-gem "wdm", "~> 0.1.0" if Gem.win_platform?
+gem "wdm", "~> 0.1", :platforms => [:mingw, :x64_mingw, :mswin]
+

_config.yml

@@ -18,6 +18,7 @@ tag_page_dir: posts/tag
 tag_permalink_style: pretty
 
 # Build settings
+theme: minima
 markdown:           kramdown
 highlighter: rouge
 paginate:           5