9.1.0

Added

• Ability to merge registries

Changed

• Correct typedefs for object constructor of metrics

9.0.0

Added

• Support for multiple registers
• Support for object literals in metric constructors
• Timestamp support

Changed

• Collection of default metrics is now disabled by default. Start collection by
  running collectDefaultMetrics().

Deprecated

• Creating metrics with one argument per parameter - use object literals
  instead.