Multiple audio stream playback, volume control, pausing

* Fix Speaking state, use latest voice API version

* Speaking state would remain stuck on after playing particularly long
stretches of audio. So far as I can tell, playing 5 frames of silence
BEFORE changing the state seems to do the trick.
* Added new constant to make sure the library uses v3 of the voice api,
which it is written for.
* Heartbeat interval adjusted by * .75 as recommended by Discord.

* Initial version of new Audio wrapper.

* Single audio file case, as before..

* Loop over all available audio samples.

* Combine audio streams, account for volume.

* Cheaper explicit Opus silence frames.

As per Discord's recommendation, use a well-known 3-byte silence frame when needed.

* A bit of cleanup

Cleanup some of the code, rename some short-form fields to longer forms
(e.g. `s/src/source`), and remove a breaking change.

`Handler::play` was changed to return `LockedAudio` instead of `()`. If
someone were to rely on `Handler::play` returning `()`, the return type
change would break their code. Instead, this functionality has been
added to a new `Handler::play_returning` function.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/constants.rs b/src/constants.rs
index 9f1807a..c9f22ac 100644
--- a/src/constants.rs
+++ b/src/constants.rs
@@ -5,6 +5,8 @@ pub const EMBED_MAX_LENGTH: u16 = 6000;
 /// The gateway version used by the library. The gateway URI is retrieved via
 /// the REST API.
 pub const GATEWAY_VERSION: u8 = 6;
+/// The voice gateway version used by the library.
+pub const VOICE_GATEWAY_VERSION: u8 = 3;
 /// The large threshold to send on identify.
 pub const LARGE_THRESHOLD: u8 = 250;
 /// The maximum unicode code points allowed within a message by Discord.