* Refactor datasets
* Update evaluators
* Update trainers
* Update main and MP-CNN model
* Add serialization util
* Fix bugs
* Refactoring for NCE to use new parent class
* update nce-sm
* refactor code, update torchtext
* use shared evaluation
* refactor code, use shared data loader
* refactor code
* refactor code
* refactor code according to Michael's great suggestions
* update readme and requirement
* update datasets and readme
* update data loader
* add space between +
* Add TrecQA dataset and modularize MP-CNN infra
* Stylistic improvements
* Fix and warn about trec_eval path issue
* Update README for MP-CNN
* Update incorrect map/mrr
* MP-CNN: address code review comments
* Create common Castor pair Dataset class
* Move map and mrr computation to Castor utils
* Make map mrr utility trec_eval path more general