Update knapsack_pro to 0.19.0
Update knapsack_pro to 0.19.0

KnapsackPro/rails-app-with-knapsack_pro,KnapsackPro/rails-app-with-knapsack_pro,KnapsackPro/rails-app-with-knapsack_pro,KnapsackPro/rails-app-with-knapsack_pro