Update package.json

actioncable/package.json

 {
   "name": "actioncable",
-  "version": "5.0.0-rc1",
+  "version": "5.1.0-beta1",
   "description": "WebSocket framework for Ruby on Rails.",
   "main": "lib/assets/compiled/action_cable.js",
   "files": [

actionview/package.json

 {
   "name": "rails-ujs",
-  "version": "0.0.1",
+  "version": "5.1.0-beta1",
   "description": "Ruby on Rails unobtrusive scripting adapter",
   "main": "lib/assets/compiled/rails-ujs.js",
   "files": [