Update: GooAQ - add train/val/test splits
@albertvillanova my tests are failing here:
```
dataset_name = 'gooaq'

    def test_load_dataset(self, dataset_name):
        configs = self.dataset_tester.load_all_configs(dataset_name, is_local=True)[:1]
>       self.dataset_tester.check_load_dataset(dataset_name, configs, is_local=True, use_local_dummy_data=True)

tests/test_dataset_common.py:234: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
tests/test_dataset_common.py:187: in check_load_dataset
    self.parent.assertTrue(len(dataset[split]) > 0)
E   AssertionError: False is not true
```
When I try loading dataset on local machine it works fine. Any suggestions on how can I avoid this error? Thanks for the help, @albertvillanova! All tests are passing now.
[GooAQ](https://github.com/allenai/gooaq) dataset was recently updated after splits were added for the same. This PR contains new updated GooAQ with train/val/test splits and updated README as well.