v0.6.0 beta 2

• Remove Clock and Clocks from the public API
• Sounds and effects now have an on_clock_tick callback instead of having a &Clocks argument passed into process
• Remove parameters
• Settings that were previously Values can now be tweened directly without needing to link them to a parameter
• All functions that send commands to the renderer now use CommandError as their error type
• Effects now have a similar structure to sounds
  • EffectBuilder - trait for types that can be converted to an Effect and a handle
  • Effect - runs on the renderer
• TrackSettings is now TrackBuilder. Effects can be added by passing an EffectBuilder to TrackBuilder::add_effect.
• Changes to the built-in effects:
  • Removed Distortion from the public API, DistortionSettings is now DistortionBuilder, added DistortionHandle
  • Removed Delay from the public API, DelaySettings is now DelayBuilder, added DelayHandle
  • Removed Reverb from the public API, ReverbSettings is now ReverbBuilder, added ReverbHandle
  • Removed Filter from the public API, FilterSettings is now FilterBuilder, added FilterHandle
• Renamed Tweenable to Tweener
• Added a Tweenable trait for things that a Tweener can control. Tweener is now generic over the type of the Tweenable value
• Volume settings now use the Volume type instead of f64
• Playback rate settings now use the PlaybackRate type instead of f64
• Clock speed settings now use the ClockSpeed type instead of f64
• Fix audio artifacts when a static sound loops
• Slight performance improvement when sounds are center-panned
• Allow configuring the main mixer track using a TrackBuilder in AudioManagerSettings