add cancancan ability for creating transactions

app/controllers/transactions_controller.rb

@@ -1,4 +1,5 @@
 class TransactionsController < ApplicationController
+  load_and_authorize_resource
   skip_before_filter :verify_authenticity_token, only: :create
 
   before_action :authenticate_user!, except: :create

app/models/ability.rb

@@ -8,6 +8,7 @@ class Ability
       can :manage, :all
     else
       can :read, user, id: user.id
+      can :create, Transaction, debtor: user
     end
   end
 end