[AIRFLOW-469] Add MFG Labs as Airflow user

Hello.

We'd like to be added as official Airflow users.

Regards

Closes apache#1768 from dud225/patch-1

README.md

@@ -110,6 +110,7 @@ Currently **officially** using Airflow:
 1. [Lucid](http://luc.id) [[@jbrownlucid](https://github.com/jbrownlucid) & [@kkourtchikov](https://github.com/kkourtchikov)]
 1. [Lyft](https://www.lyft.com/)[[@SaurabhBajaj](https://github.com/SaurabhBajaj)]
 1. [Markovian](https://markovian.com/) [[@al-xv](https://github.com/al-xv), [@skogsbaeck](https://github.com/skogsbaeck), [@waltherg](https://github.com/waltherg)]
+1. [MFG Labs](https://github.com/MfgLabs)
 1. [Nerdwallet](https://www.nerdwallet.com)
 1. [Postmates](http://www.postmates.com) [[@syeoryn](https://github.com/syeoryn)]
 1. [Qubole](https://qubole.com) [[@msumit](https://github.com/msumit)]