add doc for erf into index

add gelu into document index (for both english and chinese doc)

* Add Chinese Doc for cond API

* add Chinese document of control flow API case and switch_case. test=develop

* polish TypeError according to reviews. test=develop

As the title

* fix-apis-develop

* fix-one-error

* test=document_preview

* 0823 update FluidDoc,test=document_preview

* add two files

* ok

* ok

* ok

* add check_approval

* check approval

* check approval

* check approval

* check approval

* check approval

* check approval

* add check_approval

* add check_approval

* add check_approval

* add check_approval

* add check_approval

* change api

* change api

* split layers,test=develop

* split nn layers

* remove nn header, test=develop

* update en api doc

* update Paddle commitid

This reverts commit 76d8f574.

* update_commitid_Paddle_0428

* run gen_doc

* update_Paddle

* update_book

* update_to_1.4

* remove v2

* remove mobile

* check_1.3_api_update

* add_api_cn (#437)

* add gpu benchmark page (#436)

* add gpu benchmark

* fix comments

* add chinese link in gen_doc.py (#439)

* modified gen_doc.py

* Update gen_doc.py

* update gen_doc.py

* Update mobile doc (#440)

* update_en_structure

* update_Paddle_commitid

* delete_DS

* update_mobile_doc

* Update book commit (#438)

* update_en_structure

* update_Paddle_commitid

* delete_DS

* update_book_commit_id

* update_api_rst

* Adjust structure of advanced usage (#442)

* adjust_structure_of_advanced_usage

* Update paddle_gpu_benchmark.md

* adjust_toctree_hidden

* fix_api_guide

* Update index.rst

* fix deadlinkes (#443)

* add_toctree (#445)

* adjust_beginners_structure (#446)

* adjust_beginners_structure

* Update index.rst

* update install_doc for python3 (#418)

* update install_doc for python3

* update python3.5+ info,test=develop

* fix review, test=develop

* fix_pic (#447)

* delete en2zn link

* update lod_tensor

* 1207

 1.english api reference links removed
2. formatted

* update transpiler

* update profilse_cn

* Update docker-image instroduce, test=develop (#459)

* fix_bug (#460)

* [cp2dev]Add avx info 1.1 (#279) (#451)

* Add avx info 1.1 (#279)

* refine avx info representation

* refine avx info representation

* refine avx info representation

* updatetoavx

* fix_AVX

* update_en_api (#461)

* update api guides for cn (#462)

* Update commit_id of Paddle (#463)

* update_en_api

* update_again

* Fix bug (#465)

* update_en_api

* update_again

* bug_fix

* fix_2nd

* add_api_cn (#437)

* add gpu benchmark page (#436)

* add gpu benchmark

* fix comments

* add chinese link in gen_doc.py (#439)

* modified gen_doc.py

* Update gen_doc.py

* update gen_doc.py

* Update mobile doc (#440)

* update_en_structure

* update_Paddle_commitid

* delete_DS

* update_mobile_doc

* Update book commit (#438)

* update_en_structure

* update_Paddle_commitid

* delete_DS

* update_book_commit_id

* update_api_rst

* Adjust structure of advanced usage (#442)

* adjust_structure_of_advanced_usage

* Update paddle_gpu_benchmark.md

* adjust_toctree_hidden

* fix_api_guide

* Update index.rst

* fix deadlinkes (#443)

* add_toctree (#445)

* adjust_beginners_structure (#446)

* adjust_beginners_structure

* Update index.rst

* update install_doc for python3 (#418)

* update install_doc for python3

* update python3.5+ info,test=develop

* fix review, test=develop

* fix_pic (#447)

* Start over

* Added basic docs
Added .travis.yml
Added scripts to build documentation on the Travis.

* Disable several deploy script commend for testing.

* fixed the deploy_docs.sh script.

* Update travis.yml

* Renamed docs to doc

* update .gitignore.

* Delete .gitignore

* Update .travis.yml

* Update .travis.yml

* Update deploy_docs.sh

* Update .travis.yml

* Develop doc (#1)

* Add paddle submodule

* Update the build script.

* Update script

* Use gen_doc_lib instead.

* Move files around

* cache external

* Update submodule

* try to cache batch 1

* add test code

* Update Paddle submodule

* Update submodule

* update script to print more

* update python path

* test

* test

* test

* clean up the code

* Update Script (#2)

* add new file

* Develop doc (#3)

* Add the rest of the submodules into the system

* Provide first symlink fit a line

* Update the rest of book to symlinks

* add models submodule

* Add link for models

* Update deploy_docs