0.2.0

prometheus-client

• Add the histogram metric type (#15).
• A monitoric clock is used for duratoin measurments instead of UTCTime (#9, #16).

wai-middleware-prometheus

• Time measurments are now exported as seconds instead of microseconds (#17).
• Histograms are used instead of summaries for time measurments. This allows for
  aggregration across multiple processes (#18).