Remove reliance on nokogiri and other tools

lib.nix

@@ -3,7 +3,6 @@
 with pkgs;
 
 let
-  requiredPackages = import ./required-packages.nix { inherit pkgs nodejs; };
   website = settings: stdenv.mkDerivation {
     inherit (settings) src ssl host;
     name = "blog-static";
@@ -17,11 +16,7 @@ let
     extraFlags = if settings.drafts then " -D " else "";
     builder = ./build/builder.sh;
     buildInputs = [
-      hugo nodejs katex-html
-      requiredPackages."katex-0.11.1"
-      requiredPackages.express
-      requiredPackages.body-parser
-      (ruby.withPackages (ps: [ ps.nokogiri ]))
+      hugo katex-html
     ];
   };
   wrapHost = ssl: host: (if ssl then "https" else "http") + "://${host}";