New updates

New updates

Update metrics and figure in readme.

设置了模板，对fastNLP文件夹下的内容生成了文档

- move preprocess.py from loader/ to core/
- changes to interface of preprocess: 1. add run method, to run the main processing 2. add cross validation split 3. add return value 4. merge subclasses
- Trainer supports cross validation
- add data as arguments in Trainer.train & Tester.test
- add readme.example.py, to run the example program shown in README.md
- other corresponding changes

Updates to cores, loader, saver

Update .travis.yml

add a new chinese word segmentation model

- see fastNLp/saver/logger.py to know how to create and use a logger
- a log file named "train_test.log" will be created in the same dir as the main file where the program starts
- this file records all important events happened in Trainer & Tester's methods

Update readme, conv and max_pool

Update issue templates

# Conflicts:
#	fastNLP/core/metrics.py
#	fastNLP/core/predictor.py

- rename Inference to Predictor
- rename Trainer.prepare_input to Trainer.load_train_data, load data_train.pkl only
- add __contains__ method to config Section class
- more code comments
- more elegant make_batch & data_iterator: Samplers return batch samples instead of batch indices

Dev/ci test

Create CODE_OF_CONDUCT.md

Dev/ner

- fastNLP interface for sequence labeling works
- fastNLP interface for text classification works

Dev/classify

- rename "POSTrainer", "POSTester" to "SeqLabelTrainer", "SeqLabelTester"
- Trainer & Tester have NO relation with Action
- Inference owns independent "make_batch" & "data_forward"
- Conversion to Tensor & go into cuda are done in "make_batch"
- "make_batch" support maximum/minimum length

- rename "POSTrainer" to "SeqLabelTrainer"
- add text classification test data
- update make_batch in  Trainer and Tester

add metrics

fix optimizer

- change parameter <seq_length-->mask> in loss function defined in seq model
- Trainer & Tester have Action as default parameter, shared static methods like make_batch
- add seq_len in make_batch of Inference
- add SeqLabelInfer, a subclass of Inference
- seq_labeling.py works

- Action collects shared operations: data_forward, mode, pad, make_batch
- Trainer and Tester receives Action as a parameter
- seq_labeling works in such setting