Merge pull request #806 from MFraters/update_authors_file

Update authors file with new developers.

AUTHORS

@@ -1,4 +1,13 @@
-The Geodynamic World Builder is currently maintained and developed by Menno Fraters. 
+The development of the Geodynamic World Builderis currently lead by Menno Fraters.
+
+The following people currently serve as GWB developers -- people who have and are providing substantial technical contributions to the Geodynamic World Builder:
+
+- Juliane Dannberg (GEOMAR Helmholtz Centre for Ocean Research, Germany)
+- Daniel Douglas (New Mexico Tech, USA)
+- Menno Fraters (Geoforschungszentrum Potsdam, Germany)
+- Rene Gassmoeller (GEOMAR Helmholtz Centre for Ocean Research, Germany)
+- Timo Heister (Clemson University, USA)
+- Arushi Saxena (UC Davis, USA)
 
 There have been contributions on the development from:
   Wolfgang Bangerth,