Fix some install package errors.

* Mount local Paddle instead of git clone from remote.
* Use official chinese ubuntu source instead of 163 mirror.

Bumping up version number to v0.9.0a0

Fix forwardTest for ids in python swig.

* unittest need to be added. But fix the bugs first.

Feature/pre commit hooks scripts

Add ScalingProjection

Change-Id: Ic80845c892c96c37a0df0ddc433fe1aeaa5a9d1c

out = w * input
where w is a parameter of size 1

Change-Id: Ife682d62323ceb1a20cbbf6269421b20a862d888

Revert "fix url of sub-pages"

modify document directory structure in model config helpers

fix url of sub-pages

Added a Resnet example to quick_start demo 

Bug fix in testing mode.

* Check all files by pre commit hooks

* Add yapf hook to format python code.
* Add Remove CRLF

format python code in demo, doc, doc_cn and paddle directories

multi_binary_cross_entropy when ids vector is provided

format python code in python directory

use yapf to format python code, add style config file

Add checkout name for Dockerfile

Feature/fix pydataprovider multiple obj bugs

* Fix #436

fix test_layerHelpers unittest error