Update CONTRIBUTORS file with new team members.

CONTRIBUTORS

diff --git a/CONTRIBUTORS b/CONTRIBUTORS
index 5578a2b..c9d49ab 100644
--- a/CONTRIBUTORS
+++ b/CONTRIBUTORS
@@ -12,7 +12,10 @@
 Damien Martin-Guillerez <dmarting@google.com>
 David Z. Chen <dzc@google.com>
 Dmitry Lomov <dslomov@google.com>
+Florian Weikert <fwe@google.com>
+Jakob Buchgraber <buchgr@google.com>
 Kristina Chodorow <kchodorow@google.com>
 Laszlo Csomor <laszlocsomor@google.com>
 Lukacs T. Berki <lberki@google.com>
+Philipp Wollermann <philwo@google.com>
 Yun Peng <pcloudy@google.com>