GRN2-45, GRN2-197: Upgrade Rails to 5.2.3 and removed sass-rails gem (#636)

* Removed deprecate sass-rails and replace with sassc-rails

* Upgraded to Rails 5.2.3

* Fixed travis

* Added back Spring code

* Fixed travis again

bin/yarn

@@ -0,0 +1,13 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+APP_ROOT = File.expand_path('..', __dir__)
+Dir.chdir(APP_ROOT) do
+  begin
+    exec "yarnpkg", *ARGV
+  rescue Errno::ENOENT
+    warn "Yarn executable was not detected in the system."
+    warn "Download Yarn at https://yarnpkg.com/en/docs/install"
+    exit 1
+  end
+end