SqueezeBERT architecture (#7083)

* configuration_squeezebert.py

thin wrapper around bert tokenizer

fix typos

wip sb model code

wip modeling_squeezebert.py. Next step is to get the multi-layer-output interface working

set up squeezebert to use BertModelOutput when returning results.

squeezebert documentation

formatting

allow head mask that is an array of [None, ..., None]

docs

docs cont'd

path to vocab

docs and pointers to cloud files (WIP)

line length and indentation

squeezebert model cards

formatting of model cards

untrack modeling_squeezebert_scratchpad.py

update aws paths to vocab and config files

get rid of stub of NSP code, and advise users to pretrain with mlm only

fix rebase issues

redo rebase of modeling_auto.py

fix issues with code formatting

more code format auto-fixes

move squeezebert before bert in tokenization_auto.py and modeling_auto.py because squeezebert inherits from bert

tests for squeezebert modeling and tokenization

fix typo

move squeezebert before bert in modeling_auto.py to fix inheritance problem

disable test_head_masking, since squeezebert doesn't yet implement head masking

fix issues exposed by the test_modeling_squeezebert.py

fix an issue exposed by test_tokenization_squeezebert.py

fix issue exposed by test_modeling_squeezebert.py

auto generated code style improvement

issue that we inherited from modeling_xxx.py: SqueezeBertForMaskedLM.forward() calls self.cls(), but there is no self.cls, and I think the goal was actually to call self.lm_head()

update copyright

resolve failing 'test_hidden_states_output' and remove unused encoder_hidden_states and encoder_attention_mask

docs

add integration test. rename squeezebert-mnli --> squeezebert/squeezebert-mnli

autogenerated formatting tweaks

integrate feedback from patrickvonplaten and sgugger to programming style and documentation strings

* tiny change to order of imports

templates/adding_a_new_model/README.md

@@ -21,7 +21,7 @@ For a quick overview of the general philosphy of the library and its organizatio
 
 # Typical workflow for including a model
 
-Here an overview of the general workflow: 
+Here an overview of the general workflow:
 
 - [ ] Add model/configuration/tokenization classes.
 - [ ] Add conversion scripts.
@@ -69,7 +69,7 @@ Here is the workflow for documentation:
 - [ ] Create a new page `xxx.rst` in the folder `docs/source/model_doc` and add this file in `docs/source/index.rst`.
 
 Make sure to check you have no sphinx warnings when building the documentation locally and follow our
-[documentaiton guide](https://github.com/huggingface/transformers/tree/master/docs#writing-documentation---specification).
+[documentation guide](https://github.com/huggingface/transformers/tree/master/docs#writing-documentation---specification).
 
 ## Final steps