ERASER Camera Ready

- Fixes a bug in the released code that made reproduction of BERT-BERT models
  impossible (misspecified type of mask tensor)
- Adds parameters and reproduction instructions for BERT-BERT models
- Adds a soft-selection model for CoS-E/e-SNLI in BERT-BERT style. Adds a super
  special hack to allow processing CoS-E and CoS-E like datasets.
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# Changes to be committed:
#	modified:   README.md
#	new file:   REPRODUCTION.txt
#	new file:   params/boolq_soft.json
#	new file:   params/cose_bert.json
#	new file:   params/esnli_bert.json
#	modified:   params/evidence_inference_bert.json
#	new file:   params/evidence_inference_soft.json
#	new file:   params/fever_soft.json
#	new file:   params/movies_soft.json
#	new file:   params/multirc_soft.json
#	modified:   rationale_benchmark/metrics.py
#	new file:   rationale_benchmark/models/encode_attend.py
#	modified:   rationale_benchmark/models/mlp.py
#	modified:   rationale_benchmark/models/model_utils.py
#	modified:   rationale_benchmark/models/pipeline/bert_pipeline.py
#	modified:   rationale_benchmark/models/pipeline/evidence_classifier.py
#	modified:   rationale_benchmark/models/pipeline/evidence_identifier.py
#	new file:   rationale_benchmark/models/pipeline/evidence_token_identifier.py
#	modified:   rationale_benchmark/models/pipeline/pipeline_train.py
#	modified:   rationale_benchmark/models/pipeline/pipeline_utils.py
#	new file:   rationale_benchmark/models/sequence_taggers.py
#	modified:   rationale_benchmark/utils.py
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