- improve code comments
- BaseLoader & its subclasses does not need a data name any more
- update file tree
- add setup.py

[add] PeopleDailyCorpusLoader, to parse PeopleDaily Corpus
[update] add CWS + POS_tag interface at FastNLP, see example in test_fastNLP.py
[update] modify README.md and readme_example.py to the latest version.

- 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