Introduce an association between User and Event

Introduce an association between User and Event for the user schedule. As there was already a relation call users in Event the new relation is called public_users. And for the same reason the relation in Event is called public_events.

db/migrate/20160811143427_create_events_users.rb

@@ -0,0 +1,8 @@
+class CreateEventsUsers < ActiveRecord::Migration
+  def change
+    create_table :events_users, id: false do |t|
+      t.references :event
+      t.references :user
+    end
+  end
+end