Update .gitignore file.

Former-commit-id: a8420c30693eb6b7183e8f00491c7d4638a356e9

.gitignore

@@ -78,3 +78,5 @@ tutorial/XXX_test/main.cpp
 python/py_igl/todo
 python/build
 python/.idea
+tests/build
+tests/bin