* Add usage manual for VisualDL
The usage manual will be helpful for beginners to make use of VisualDL.

Components of VisualDL are introduced in details, including:
	* Definition of Functions
	* Parameters explanation
	* Demo program for each component

* add_index

* synchronize with develop (#642)

* update_commitid1.3 (#641)

* update inference c++ API doc (#634)

* update inference c++ API doc

* fix link

* thorough clean for doc (#644)

* thorough clean

* delete_DS_Store

* Cherrypick1.3 (#652)

* thorough clean

* delete_DS_Store

* [Don't merge now]update_install_doc (#643)

* update_install_doc

* follow_comments

* add maxdepth (#646)

* upload_md (#649)

* update_version (#650)

* Translation of 16 new apis (#651)

* fix_windows

* Final update 1.3 (#653)

* thorough clean

* delete_DS_Store

* update_1.3

* Deadlink fix (#654)

* fix_deadlinks

* update_docker

* Update release_note.rst

* Update index_cn.rst

* update_Paddle (#658)

* fix pic (#659)

* [to 1.3] cn api debug (#655) (#661)

* debug

* fix 2 -conv2d

* "锚" ==> anchor(s)

* 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