* Fix doc format for callbacks, metrics and Model
* Fix code sample and doc

* Move hapi form paddle/incubate to paddle

* Remove vision/datasets/utils.py and clean code

* Add sample code for conll05

* Print pull path when saving model

* Fix sample code after paramter_list of SGD is changed to parameters

* Fix bug in wmt16 datase

* fix RandomSampler & BatchSampler. test=develop

* add Sampler/SequenceSampler/RandomSampler. test=develop

* add IterableDataset support in multiprocess DataLoader. test=develop

* add DataLoader, Dataset, BatchSampler