Add GLUE Compat (compatible with transformers<3.5.0)
Maybe it would be simpler to just overwrite the order of the label classes of the `glue` dataset ?
```python
mnli = load_dataset("glue", "mnli", label_classes=["contradiction", "entailment", "neutral"])
``` Sounds good. Will close the issue if that works.
Link to our discussion on Slack (HF internal)
https://huggingface.slack.com/archives/C014N4749J9/p1609668119337400

The next step is to add a compatible option in the new `run_glue.py`

I duplicated `glue` and made the following changes:
1. Change the name to `glue_compat`.
2. Change the label assignments for MNLI and AX.