Makefile prereq additions and change to protos Makefile to use the publicly accessible git repository

Change-Id: I115983dd566b316d59be51623a22a4e35a9be250
diff --git a/protos/Makefile b/protos/Makefile
index ba9591f..046ca49 100644
--- a/protos/Makefile
+++ b/protos/Makefile
@@ -40,7 +40,7 @@
 
 googleapis:
 	if [ ! -e "googleapis" ]; then \
-		git clone git@github.com:googleapis/googleapis.git; \
+		git clone https://github.com/googleapis/googleapis.git; \
 		make -C googleapis LANGUAGE=cpp all; \
 	fi;