Add avg_cost and ppl for Transformer

Refine the inference to output special tokens optionally in Transformer

Adapt usage of reduce_mean to the latest fluid API.

Fix data feed in test & profile

update IP to new node

Modify gradient method, add README.md and tutorials in advbox

Replace v2.dataset with dataset in Transformer

Refine OCR CTC model.

Replace cross_entropy with softmax_with_cross_entropy in Transformer

data load for inference

Fix the softmax in Transformer.

Add decoder init & verify output

Expose acoustic scale in decoder