Add mixer fixedvol

[sashahilton00]

Issue by mattiash
Tuesday Mar 14, 2017 at 19:56 GMT
Originally opened as plietar/librespot#163

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Add a new mixer that always outputs sound at 100% volume. To print the current volume that spotify requests, set RUST_LOG=librespot::mixer::fixedmixer=debug

This PR can be applied instead of PR #161 .

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mattiash included the following code: https://github.com/plietar/librespot/pull/163/commits

[ComlOnline]

@mattiash Could you please submit another PR to this repo? Thanks