modify readme example

add MLP decoder

New Trainer Initialization Interface

- add Loss, Optimizer
- change Trainer & Tester initialization interface: two styles of definition provided
- handle Optimizer construction and loss function definition in a hard manner
- add argparse in task-specific scripts. (seq_labeling.py & text_classify.py)
- seq_labeling.py & text_classify.py work

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