v5.0.1

Bug fix release for mimetypes

Python's mimetypes module is incomplete and doesn't include enough extensions, so I hardcoded the valid FFmpeg audio encoder extensions to check against this time when loading an audio_file.

Should fix cases where .aac and others were recognized as an invalid file extension, or raised a KeyError when searching for these extensions in the mimetypes.types_map dict.

Minor changes:

If the file extension is not recognized as being supported by one of FFmpeg's encoders, it will automatically change the outfile extension to WAV and re-encode losslessly to waveform (using pcm_s16le codec).