Bug fix and refine cloud training for DS2

Summary:
1. Add missing is_local argument (when set False, use pserver).
2. Add exception thrown if cp failed.
3. Add cloud mkdir if not cloud path for uploading does not exist.
4. Fix a bug using common path ./local_manifest for all nodes. (convert to /local_manifest)
5. Refine coding style.

Fix  local data variable in DS2 data generator.

Add code adaptation to enable DS2 to run on PaddleCloud.

1. Refine data_utils/data.py, reuse process_utterance function.
2. Modified README.
3. Implement uploading data in cloud/upload_data.py
4. Merge branch 'develop' of https://github.com/PaddlePaddle/models into ds2_pcloud

Add download url.

Add demo for SSD model (WIP)

Update readme in DS2

Update mfcc computation in DS2

Add vocabulary dictionary building script

Unify encoding to 'utf-8' and optimize error rate calculation.

Make type of error rate optional.

Add NoisePerturbAugmentor and CHiME3 noise data preparation.