* add releasenotes and models

* add releasenotes en version

* dygraph translation

* cn doc bug fix

* translate dygraph according to 1.5.1 website + bug fix

* update 1.5.1 cn API

* add url

* test=develop, add fix_install_doc_with_gpu_docker_usage (#1007)

* test=develop, add fix_install_doc_with_gpu_docker_usage

* refine format

* fix install command wrong

* fix some problem in install doc (#1008)

* add windows install whl

* whl and bug

* fix some bugs

compile_CentOS.md
compile_Ubuntu.md
install_CentOS.md
install_Ubuntu.md

* add best practice

* polish doc

* add retinanet_target_assign + focal_loss (#969)

* break up layers and change index of layers (#970)

* break up layers and change index of layers

* prettify script

* bugfix

* Update release_note_cn.rst

* update api_cn; fix the error of reverting layers_cn to 1.4; include previous changes

* update layers_cn; add code example to elementwise_mod

* delete recordio_writer_cn; revert index_cn

* update api_cn after review

* fix io_cn.rst

* update layers_cn

* update io_cn

* add lite

* lite clean

* update

* up

* update

* refine lite mobile doc (#962)

* update

* update

* test=develop, update install doc

* add setuptools dependency

* Update compile_Ubuntu.md

update cudnn version

* Update install_Ubuntu.md

update cudnn version

* Update install_CentOS.md

update cudnn version

* test=develop, refine ubuntu cuda support

* test=develop, refine ubuntu cuda support

* test=develop, refine python support on python3.5

* fix python2 in ubuntu16.04 need gcc 5.4

* add nccl related doc

* refine doc

* add gpu fast install doc

* refine command of pip

* add avx off for mac complie

* refine code

* refine doc

* fix python only support 64bit

* update urls for x2paddle

* Update TensorFlow-Fluid.rst

* Update TensorFlow-Fluid.rst

* Update TensorFlow-Fluid.rst

* Update TensorFlow-Fluid.rst

* Update TensorFlow-Fluid.rst

* Update TensorFlow-Fluid.rst

* update paddle-mobile doc

* delete untracked file

* add install appendix

* add install appendix

* add install appendix

* add install appendix

* update mobile according to paddle-mobile repo

* Update mobile_readme_en.md

1.add dygraph api doc
2.add dygraph node

* update paddle-mobile doc

* delete untracked file

* documents will be ready afterwards

not ready now

* Update index_en.rst

* Update index_cn.rst

* Update index_en.rst

* Update index_cn.rst

* Update index_en.rst