AudioSystem Proposal

[otraore]

We've decided to create a new audio package engo.io/audio which is similar to engo.io/gl being a wrapper around the audio players for each platform. It'll have a higher level API similar to https://godoc.org/golang.org/x/mobile/exp/audio. After it's done the AudioSystems will be using it to provide a cross-platform audio player/system. This will also attempt to support the AudioSystem on both the web and windows targets.

[otraore]

Going to give a shot at windows audio using: https://bitbucket.org/StephenPatrick/go-winaudio/src

[otraore]

Update: I've been working on windows audio using this branch/pr. I've got it to work using another wav file other than the previous birds.wav file. Setting the volume isn't properly working either. It is playing on windows though. I'm using the built-in audio package demo to test it out. I'll update this PR as progress occurs.

Edit: Since I didn't mention it on this issue before, web audio is also working properly although it's not using 3d audio.

Edit2: Windows Audio is using DirectSound

[Noofbiz]

Closed in #494