enable multiprocessing feature on master

Author: ludlows

README.md

@@ -75,7 +75,7 @@ print(pesq(rate, ref, deg, 'wb'))
 print(pesq(rate, ref, deg, 'nb'))
 ```
 
-# Usage for batch version
+# Usage for `multiprocessing` feature
 
 ```python
 def pesq_batch(fs, ref, deg, mode='wb', n_processor=None, on_error=PesqError.RAISE_EXCEPTION):

pesq/__init__.py

@@ -4,3 +4,5 @@
 
 from ._pesq import pesq, pesq_batch
 from ._pesq import PesqError, InvalidSampleRateError, OutOfMemoryError, BufferTooShortError, NoUtterancesError
+__all__ = ['pesq', 'pesq_batch',
+           'PesqError', 'InvalidSampleRateError', 'OutOfMemoryError', 'BufferTooShortError', 'NoUtterancesError']