[ENHANCEMENT] Be more resilient to certain file corruptions (#329)
[ENHANCEMENT] Permit subclassing of MetricsHandler (#339)
[ENHANCEMENT] Updates based on latest OpenMetrics draft spec discussions (#338 #346)
[BUGFIX] In multiprocess mode, ensure that metrics initialise to the correct file (#346)
[BUGFIX] Avoid re-entrant calls to GC collector's callback (#343)