Cleaned up convert.py and renamed it to decode.py

- 'Converter' class removed
- 'ensure_folder' removed
- 'find_files' changed into a generator and made it work with spaces
- 'convert' renamed into 'read'
- 'convert' now handles any supported file by pydub
- 'convert' now returns the data instead of saving it to a file (same format as 'extract_channels')
- generic cleanup of formatting in the file
Added the fix for issue #13 in the original repository.
Fixed any references to old converter to use the new functions.

- Reversed return values in decode.read