Update authors

AUTHORS

 Active Kdenlive authors
 
-    Vincent Pinon <vpinon@april.org>
-        Bugs fixing, release
-        2012-present
     Jean-Baptiste Mardelle <jb@kdenlive.org>
-        MLT and KDE SC 4 porting, main developer
+        Main developer and maintainer, MLT and KDE SC 4 / KF5 port, 
         2005-present
+    Vincent Pinon <vpinon@kde.org>
+        Interim maintainer, Windows cross-build, KF5 port, profiles updates, etc.
+        2012-present
+
+Former Kdenlive authors
+
     Laurent Montel <montel@kde.org>
         Bugs fixing, code clean up, review
-        2013-present
+        2013-2017
     Till Theato <root@ttill.de>
         Bug fixing, etc.
-        2010-present
+        2010-2015
     Steve Guilford <s.guilford@dbplugins.com>
         Bug fixing
         2014
-
-Former Kdenlive authors
-
     Simon A. Eugster (Granjow) <simon.eu@gmail.com>
         Colour and audio scopes, titler, manual, bug fixing, etc.
         2009-2012