alternative front-end that processes remote rather than local files

[gabe97330]

I have a use case where the files to be fingerprinted are not local and it it would be ideal to be able to pipe the minimum number of bytes from the remote files to the fingerprinter to do its work. In looking at the code, I'm imaging an alternative set of wrapper classes to main and AudioStreamInput that would be passed a set of url rather than a set of local files and would invoke ffmpeg passing it a stream rather than a file as input.