#487

* Check all files by pre commit hooks

* the memory leak is inside one pass.

* Use `gshuf` instead of `shuf` in macOS
* Fix #388

* Fix SRL hang when exit.

* Error occurred when enable Async Load in TestDataProvider.
  * It because DataProvider is calling getNextBatchInternal in one thread, and destructing DataProvider in other thread.
  * Add wait routine in DataProvider destructing.
* Also fix another bug, when destructing TestDataProvider and do not read any test data.

Fix #286

* Follow comments, Use mutex is cool!

* Python trainer API and demo

* Adding missing PaddleAPIPrivate.h

* Adding api_train.sh

* More comments

* Bump up patch version to 0b3

* fix error in doc of quick_start
* There are some warning when execute preprocess.sh 

* Fix bug in yield dictionary in DataProvider.
* Also make virtualenv work in Paddle.

* added mnist demo

* modified .gitignore for .project files

* normalize pixel in mnist_provider.py and set use_gpu=0