Merge pull request #4913 from pszemus/master

Update protobuf version to v3.0.0-beta-2

.gitmodules

@@ -4,7 +4,7 @@
 [submodule "third_party/protobuf"]
 	path = third_party/protobuf
 	url = https://github.com/google/protobuf.git
-	branch = v3.0.0-alpha-4.1
+	branch = v3.0.0-beta-2
 [submodule "third_party/gflags"]
 	path = third_party/gflags
 	url = https://github.com/gflags/gflags.git

examples/cpp/helloworld/Makefile

@@ -94,7 +94,7 @@ ifneq ($(HAS_VALID_PROTOC),true)
 	@echo "Please install Google protocol buffers 3.0.0 and its compiler."
 	@echo "You can find it here:"
 	@echo
-	@echo "   https://github.com/google/protobuf/releases/tag/v3.0.0-alpha-1"
+	@echo "   https://github.com/google/protobuf/releases/tag/v3.0.0-beta-2"
 	@echo
 	@echo "Here is what I get when trying to evaluate your version of protoc:"
 	@echo

examples/cpp/route_guide/Makefile

@@ -86,7 +86,7 @@ ifneq ($(HAS_VALID_PROTOC),true)
 	@echo "Please install Google protocol buffers 3.0.0 and its compiler."
 	@echo "You can find it here:"
 	@echo
-	@echo "   https://github.com/google/protobuf/releases/tag/v3.0.0-alpha-1"
+	@echo "   https://github.com/google/protobuf/releases/tag/v3.0.0-beta-2"
 	@echo
 	@echo "Here is what I get when trying to evaluate your version of protoc:"
 	@echo