Update paper_trail gem to latest

Gemfile.lock

@@ -254,7 +254,7 @@ GEM
       rake
     mini_magick (4.5.1)
     mini_portile2 (2.0.0)
-    minitest (5.8.4)
+    minitest (5.9.0)
     momentjs-rails (2.8.1)
       railties (>= 3.1)
     monetize (1.4.0)
@@ -302,9 +302,10 @@ GEM
       rack-openid (~> 1.3.1)
     open4 (1.3.4)
     orm_adapter (0.5.0)
-    paper_trail (3.0.1)
-      activerecord (>= 3.0, < 5.0)
-      activesupport (>= 3.0, < 5.0)
+    paper_trail (5.0.1)
+      activerecord (>= 3.0, < 6.0)
+      activesupport (>= 3.0, < 6.0)
+      request_store (~> 1.1)
     parser (2.3.0.3)
       ast (~> 2.2)
     pdf-core (0.2.5)
@@ -402,7 +403,7 @@ GEM
       yajl-ruby (~> 1.1)
     redcarpet (3.2.3)
     referer-parser (0.2.1)
-    request_store (1.0.6)
+    request_store (1.1.0)
     responders (2.1.1)
       railties (>= 4.2.0, < 5.1)
     rest-client (1.8.0)

app/controllers/application_controller.rb

@@ -1,4 +1,5 @@
 class ApplicationController < ActionController::Base
+  before_filter :set_paper_trail_whodunnit
   include ApplicationHelper
   add_flash_types :error
   protect_from_forgery with: :exception

config/initializers/paper_trail.rb

@@ -0,0 +1,2 @@
+# Tracking associations is an experimental feature and it is recommended to set it to false
+PaperTrail.config.track_associations = false