Update AUTHORS.md

Updated the list of authors.

AUTHORS.md

@@ -1,13 +1,27 @@
+This file lists the authors of the Qresp software as well as the known contributors.
+
 # Project Leads 
 
 - Marco Govoni (Argonne National Laboratory and University of Chicago)
 - Giulia Galli (University of Chicago and Argonne National Laboratory)
 
-## Developers
+# Developers
+
+The current list of developers, in alphabetical order:
 
+- Marco Govoni (Argonne National Laboratory and University of Chicago)
 - Aditya Tanikanti (University of Chicago)
 
-## Contributors
+# Former Developers
+
+The former list of developers, in alphabetical order:
+
+- Milson Munakami (2017-2018)
+
+# Contributors
+
+We would like to thank the following people for their contibution (beside generic comments and bugfixes):
+
+- Jonathan Skone (University of Chicago): for strategic discussions
 
-- Milson Munakami
-- Jonathan Skone
+Please, don't hesitate to contact us if you see that information is wrong or missing in this file.