cpal 0.5.0

Added

• EventLoop::build_voice, EventLoop::destroy_voice, EventLoop::play, and EventLoop::pause methods.
• VoiceId struct that is now used to identify a voice owned by an EventLoop.

Changed

• EventLoop::run() to take a callback that is called whenever a voice requires sound data.
• supported_formats() to produce a list of SupportedFormat instead of Format. A SupportedFormat must then be turned into a Format in order to build a voice.

Removed

• Dependency on the futures library.
• Voice and SamplesStream types.