Fix typo in DESCRIPTION

Author: dmcglinn

DESCRIPTION

@@ -8,7 +8,7 @@ Authors@R: c(person("Xiao", "Xiao", email = "[email protected]",
              person("Felix", "May", email = "[email protected]", 
                     role = "aut"),
              person("Thore", "Engel", email = "[email protected]",
-                    role = "aut")
+                    role = "aut"),
              person("Caroline", "Oliver", email = "[email protected]",
                     role = "aut"))
 Date: 2018