Feature/shuffle reader

Add product reduction for reduce op.

Enhance regularizer.py

Fix distributed train doc deadlink

Add api doc std

* "Refine nccl op"

* "refine code "

* "refine nccl code"

Merge branch 'develop' of https://github.com/PaddlePaddle/Paddle into feature/Enhance_regularizer_py

Enhance look_up_table op 

move fluid dist design to fluid folder

Feature/recordio file reader

* fix mac build error

* remove unnecessary build graph

* fix nccl op unit test

* fix build error

* format code

* refine nccl related unit test

* fix build error

* add setGPUData

* clean up

* follow comments

* rm test_nccl.cu

* follow comment

* rm wait

* add is_local paramter description

* update

* update by comment

* add sparse update section in fluid dist doc

* update by comment

* update

* update by comment

"add develop standard"

Extract Prepare from Executor

Refine the profile codes for inference.

* add memopt level

* add opt level for image classification demo

* clean code

* add delete op

* clean code

* test machine translation demo

* clean code

* clean code

* skip fill constant with force cpu

* clean code

* clean code

* refine code

* clean code

* fix bug