FLAC decoder under av/stream/flac

[Saxon Milton]

Id to propose that we create a flac package for dealing with flac encoding and decoding. In terms of encoding, if anything, it will just help to wrap stuff from https://github.com/mewkiz/flac . But decoding features will be more extensive. At least initially I will just add decoding functionality. I'm thinking it'll just be a func: func Decode(buf []byte) ([]byte, error) as well as other required structs, like an io.WriteSeeker implementation that is required to get things working with the wav package I'd like to use: https://github.com/go-audio/wav .

I've done some testing with this and have success.

[Saxon Milton]

A flac decoder has been implemented in PR #123 , however, location is under av/experimentation as it is not currently going to be useful.