To reply to Facebook Messenger push notifications -> Before this tweak,
1: Tap Notifications to open Messenger.app
3: Close Messenger.app
4: Open the previous app
With QuickReply For Messenger,
1: Tap to reply to push notifications
2: Continue using the current app
Quick Reply for Messenger has a three day trial after which the tweak costs $1.99. If you've purchased TwitkaFly your price is $0.99.
You can get the tweak from the Big Boss Cydia Repository and configure it from the Settings.app.