add dataset read functions

add SNLI model

update DataSet and DataSetLoader

Fix the demo figures in

add biaffine dependency parser & some modules

add model.fit()

update docs

update

Merge Preprocessor into DataSet.

- improve metrics codes
- fix validator bugs in trainer; remove early saving
- run CWS codes
- improve README.md

- DataSet's __init__ takes a function as argument, rather than class object
- Preprocessor is about to remove. Don't use anymore.
- Remove cross_validate in trainer, because it is rarely used and wired
- Loader.load is expected to be a static method
- Delete sth. in other_modules.py
- Add more tests
- Delete extra sample data

Final

fix bug

update

Name Changes & More Tests

- add character vocab in preprocessor
- add dataset loader for language model dataset
- other minor adjustments
- preserve only a little example data for language model

2. changes of names:
  aggregation ----> aggregator
  interaction ----> interactor
  action.py ----> sampler.py
  BasePreprocess ---> Preprocessor
  BaseTester ----> Tester
  BaseTrainer ----> Trainer
3. add more code comments
4. fix bugs in predictor's data_forward
5. in sampler.py, remove Bachifier, fix some codes. but not test
6. remove unused codes in other_modules.py & utils.py
7. update fastnlp.py with new config file names and code comments
8. add data examples in data_for_tests/

add Vocabulary

update

update MLP