Closing test coverage gap

- Modified `experiments.py` to make sure that we reject parsing config files with no `task` and `experiment_name`
- Added 3 tests to test config file parsing, to start with
- Added config file template for these tests
Much like we have in `experiments.py`, you'll want to change this to:

```python
with open(fold_file_path,  'wb' if PY2 else 'w') as fold:
```