Create a function `create_sound_stream_stereo` that creates a SoundStream

[bvssvni]

This should use Settings { sample_hz: 44100, frames: 256, channels: 2 }

[bvssvni]

One problem is that the buffer must be a multiple of the channel size. The SoundStream depends on the type of the output buffer, which depends on const BUFFER_SIZE: uint = (FRAMES * CHANNELS) as uint;. This means the type of the SoundStream depends on the number of channels you need.

[bvssvni]

Could use an enum with different types of SoundStream.

[bvssvni]

Could have a function you call with a closure that gets called on another thread. Rust moves to unboxed closures now. See rust-lang/rust#19338

piston::sound(piston::Audio::Stereo, move || {
    ...
});

[bvssvni]

This is outdated.