* add nccl related info

* refine code

* link default

* link-fault

* link-default-3

* update_to_develop

* fix

* fix_02

[cherry-pick] Fix reader.md 

* Quickstart (#544)

* upload enhowto

* upload cluster quick start en

* review commit

* recover original multi_node.rst index

* fix index of cluster_howto

* fix index

* fix bugs

* upload save_load_variables_en (#549)

* upload save_load_variables_en

* Textual Review

* upload train_on_baidu_cloud_en (#550)

* upload train_on_baidu_cloud_en

* First round review check

* review on webpage, fix minors

* upload indexen (#551)

* upload indexen

* Textual Review

* upload metricsen (#552)

* upload metricsen

* First round review

* minor fix to round 1 review

* Update metricsen.rst

* Change file name and re-review

* lod_tensor_en (#554)

* lod_tensor_en

* Textual Content Check

* Review and fix on webpage

* numpt_array_en (#555)

* numpt_array_en

* Textual Content Check

* fix wrong file location and name

* review on webpage

* simple_model (#557)

* simple_model

* Contextual Review

* review on webpage

* single_node (#558)

* single_node

* Textual Fix

* review on webpage

* test_while_training (#559)

* test_while_training

* Textual Review

Textual Fix

* py_reader_en (#564)

* py_reader_en

* Textual Check

* user guides index of all (#595)

* visualdl en +cn  official readme (#598)

* FluidModel Fix (#611)

- delete the Models index in root index
- update models/index_en.rst

Revert "update link of models"

This reverts commit 2b012ad6.

This reverts commit 7f63ba3d.

* update link of models

* update en_version

* 0123-routine-docbug-fix

* Update metrics.rst

* update_to_develop

* fix

* update_to_1.2.1

* update_to_1.2.1

* polish_win_install (#562)

* polish_win_install

* follow_comments

* update_to_1.2.1

[cherry-pick]0114-cnapi-bugfix

* update_inference_link

* delete cuda 7.5 line in table

* add&update develop table

* integration_2tables

cherry pick - cn api fix bugs (#523)

* cn api fix bugs

* Update fluid_cn.rst

* Update lod_tensor.rst

- Modify some inaccurate descriptions
- Add the complete code example

* Update lod_tensor.rst

update_submodule_1.2

remove unused inference header

[cherry-pick] Update cn_api from develop to release/1.2

[cherry-pick] fix last_step for 1.2