Created by: chrisxu2016

add data augmentation part for DeepSpeech2(inclued noise_speech, impuls_response eg)

• add data augmentation class ,inclued noise_speech, impuls_response, resampler, speed_perturb, online_bayesias_normalization.
• add function to audio.py, eg. convolve， add_noise, normalizer
• add noise data preprocess script