fix a bug in init and add dropout in MLP

fix & update batch

Add support for sorted batch output, can be useful when using RNN in Pytorch with `pack_padded_sequence` & `pad_packed_sequence`

Character-level Text Field

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