Fixed read error when initializing bytes data in Python 3

[shichao-an]

The original code will throw AttributeError: 'bytes' object has no attribute 'read' when initializing pydub.AudioSegment with a bytes object in Python 3. Since your code indends to support Python 3 by using BytesIO (aliased into StringIO), pydub.AudioSegment should have accepted bytes data.

The problematic line of code is this:

data = data if isinstance(data, basestring) else data.read()

It only checks if data is basestring, which does not exist in Python 3. If data is of bytes in Python 3, it will go to else part and failed.

Since you didn't use six, I added an extra isinstance check here to make the code change as minimal as possible, though it may not be a good enough.

FYI, my code which complains about this is here, and the error output is:

$ ./run.py
Traceback (most recent call last):
  File "./run.py", line 5, in <module>
    main()
  File "/Users/shichao/Documents/projects/soundmeter/soundmeter/meter.py", line 315, in main
    m.start()
  File "/Users/shichao/Documents/projects/soundmeter/soundmeter/meter.py", line 126, in start
    segment = pydub.AudioSegment(data)
  File "/Users/shichao/envs/soundmeter3.4/lib/python3.4/site-packages/pydub/audio_segment.py", line 130, in __init__
    data = data if isinstance(data, basestring) else data.read()
AttributeError: 'bytes' object has no attribute 'read'