Update rails, gems, use MathJax over CDN

bin/setup

@@ -1,10 +1,9 @@
 #!/usr/bin/env ruby.exe
-require 'pathname'
 require 'fileutils'
 include FileUtils
 
 # path to your application root.
-APP_ROOT = Pathname.new File.expand_path('../../', __FILE__)
+APP_ROOT = File.expand_path('..', __dir__)
 
 def system!(*args)
   system(*args) || abort("\n== Command #{args} failed ==")
@@ -21,7 +20,6 @@ chdir APP_ROOT do
   # Install JavaScript dependencies if using Yarn
   # system('bin/yarn')
 
-
   # puts "\n== Copying sample files =="
   # unless File.exist?('config/database.yml')
   #   cp 'config/database.yml.sample', 'config/database.yml'