BLUE 2
this PR seemed to be out of date due to being late considered (https://github.com/huggingface/transformers/pull/1238). 

So I updated the code to be able to merge with the latest version. 

In this PR:

- I add BertForMultiLabelClassification, RobertaForTokenClassification, RobertaForMultiLabelClassification.

- I add examples for Finetuning the BERT, RoBERTa models for tasks on BLUE (https://github.com/ncbi-nlp/BLUE_Benchmark). BLUE (Biomedical Language Understanding Evaluation) is similar to GLUE, but for Biomedical data. The "run_blue", "utils_blue" are customized from "run_glue", "utils_glue", but more sufficient, because it contains not only sequence classification, but also token classification, multi-label classification. People may also have more options for examples of fine-tuning BERT/RoBERTa.

- I also add test function to test_examples as well as test data
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/1440?src=pr&el=h1) Report
> Merging [#1440](https://codecov.io/gh/huggingface/transformers/pull/1440?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/1615360c71f75da7b8aefd14c5d8a461486f865b?src=pr&el=desc) will **decrease** coverage by `1.21%`.
> The diff coverage is `30.88%`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/1440/graphs/tree.svg?width=650&token=9qOlN6Hb1c&height=150&src=pr)](https://codecov.io/gh/huggingface/transformers/pull/1440?src=pr&el=tree)

```diff
@@            Coverage Diff            @@
##           master   #1440      +/-   ##
=========================================
- Coverage   84.72%   83.5%   -1.22%     
=========================================
  Files          84      84              
  Lines       12591   12656      +65     
=========================================
- Hits        10668   10569      -99     
- Misses       1923    2087     +164
```


| [Impacted Files](https://codecov.io/gh/huggingface/transformers/pull/1440?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [transformers/modeling\_bert.py](https://codecov.io/gh/huggingface/transformers/pull/1440/diff?src=pr&el=tree#diff-dHJhbnNmb3JtZXJzL21vZGVsaW5nX2JlcnQucHk=) | `85.54% <27.27%> (-2.63%)` | :arrow_down: |
| [transformers/modeling\_roberta.py](https://codecov.io/gh/huggingface/transformers/pull/1440/diff?src=pr&el=tree#diff-dHJhbnNmb3JtZXJzL21vZGVsaW5nX3JvYmVydGEucHk=) | `57.06% <32.6%> (-14.16%)` | :arrow_down: |
| [transformers/modeling\_tf\_pytorch\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/1440/diff?src=pr&el=tree#diff-dHJhbnNmb3JtZXJzL21vZGVsaW5nX3RmX3B5dG9yY2hfdXRpbHMucHk=) | `10.48% <0%> (-66.44%)` | :arrow_down: |
| [transformers/tests/modeling\_tf\_common\_test.py](https://codecov.io/gh/huggingface/transformers/pull/1440/diff?src=pr&el=tree#diff-dHJhbnNmb3JtZXJzL3Rlc3RzL21vZGVsaW5nX3RmX2NvbW1vbl90ZXN0LnB5) | `87.5% <0%> (-7.5%)` | :arrow_down: |
| [transformers/modeling\_xlnet.py](https://codecov.io/gh/huggingface/transformers/pull/1440/diff?src=pr&el=tree#diff-dHJhbnNmb3JtZXJzL21vZGVsaW5nX3hsbmV0LnB5) | `71.25% <0%> (-0.9%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/huggingface/transformers/pull/1440?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/huggingface/transformers/pull/1440?src=pr&el=footer). Last update [1615360...e7ffd9a](https://codecov.io/gh/huggingface/transformers/pull/1440?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
<|||||>Ok, I think this is great, sorry for the delay in reviewing the PR.<|||||>Do you want to just add the new RoBERTa models in the tests, at least [this line](https://github.com/huggingface/transformers/blob/master/transformers/tests/modeling_roberta_test.py#L38).

Also, optional but could be nice if you feel like it: add TF 2.0 counterparts to your new PyTorch heads (you can just copy-past-adapt) the relevant Bert heads.<|||||>This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.
