Update Protobuf submodule to v3.0.0 (GA)
diff --git a/.gitmodules b/.gitmodules
index 98bedad..d41b8d5 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -4,7 +4,7 @@
 [submodule "third_party/protobuf"]
 	path = third_party/protobuf
 	url = https://github.com/google/protobuf.git
-	branch = 3.0.0-beta-4
+	branch = 3.0.0-GA
 [submodule "third_party/gflags"]
 	path = third_party/gflags
 	url = https://github.com/gflags/gflags.git