Allow using ctest for testing (#29)

Author: aobolensk

README.md

@@ -22,7 +22,7 @@ $ cmake --build build --parallel
 ## Test
 
 ```bash
-$ build/bin/run_tests
+$ ctest --test-dir build
 ```
 
 ## Code coverage

test/CMakeLists.txt

@@ -4,3 +4,10 @@ add_executable(run_tests ${TEST_SRC_FILES})
 target_link_libraries(run_tests PUBLIC
     gtest_main
 )
+
+if(NOT WIN32)
+    include(GoogleTest)
+    gtest_discover_tests(run_tests)
+
+    enable_testing()
+endif()