Add Dmitry Gamza and Sebastian Leonhardt to CREDITS.

Change-Id: I10c3c8963277905f3c74247fc16acc247323e30f
diff --git a/docs/CREDITS b/docs/CREDITS
index 94e8df2..b41df32 100644
--- a/docs/CREDITS
+++ b/docs/CREDITS
@@ -633,6 +633,8 @@
 Kirill Stryaponoff
 Roman Poltoradnev
 Ryan Billing
+Dmitry Gamza
+Sebastian Leonhardt
 
 The libmad team
 The wavpack team