Improve audio featurizer and add shift augmentor for DS2.

Refine inferring of hsigmoid to avoid loading model every batch.

update inferring results for NER model in README.

rename and refine codes of hsigmoid.

refine NER.

using previous travis-ci image

1. Improve audio featurizer.
2. Add shift augmentor.
3. Update default argument to be the current best seggestion.
4. Add checkpoints with pass id.

Add multi-threading support for DS2 data generator.

refine codes of LM.

Fix ci

    1. Unify the dependency installation process in setup.sh.
    2. Change the version of package scipy from 0.13.0b1 to 0.13.1

Add some audio transformation methods to AudioSegment and SpeechSegment class.

Add error rate calculation script.

Add scheduled sampling.

    1. First install dependencies;
    2. Surpport abosulate import.