Move google test towards the external folder.

.gitmodules

@@ -1,5 +1,5 @@
 [submodule "googletest"]
-	path = googletest
+	path = external/googletest
 	url = https://github.com/google/googletest.git
 [submodule "external/protobuf"]
 	path = external/protobuf

CMakeLists.txt

@@ -5,14 +5,14 @@ project(test_EmbeddedProto)
 set(CMAKE_CXX_FLAGS "-std=c++14 -Wall")
 
 
-add_subdirectory(googletest)
+add_subdirectory(external/googletest)
 
 file(GLOB src_files
     "test/*.cpp"
 )
 
 include_directories(test src)
-include_directories(googletest/googletest googletest/googletest/include)
+include_directories(external/googletest/googletest external/googletest/googletest/include)
 
 add_executable(test_EmbeddedProto ${src_files})
 target_link_libraries(test_EmbeddedProto gtest)