Add git submodule
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..7999bfa
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,6 @@
+[submodule "3rd_party/google_test"]
+ path = 3rd_party/google_test
+ url = https://github.com/google/googletest.git
+[submodule "3rd_party/benchmark"]
+ path = 3rd_party/benchmark
+ url = https://github.com/google/benchmark.git
diff --git a/3rd_party/benchmark/downloadhere.txt b/3rd_party/benchmark/downloadhere.txt
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/3rd_party/benchmark/downloadhere.txt
diff --git a/3rd_party/google_test/downloadhere.txt b/3rd_party/google_test/downloadhere.txt
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/3rd_party/google_test/downloadhere.txt
