0.16.0

Added

• Handle to clear psutils metrics
• invoke_callbacks option for metrics.collect()
• Ability to set metainfo for collectors
• Set metainfo.default to true for all collectors
  from enable_default_metrics() and psutils collectors
• default_only option for metrics.collect()

Fixed

• Fix is_healthy function to rely on membership state
• Fix psutils time metrics
• Fix missing psutils cpu count after clear

Removed

• Set non-number values in gauge:set
• Deprecated metrics from previous releases