Changed

• Metrics library has been replaced with a new version which reduces memory footprint.
• Samplers have been optimized to reduce number of system calls and temporary allocations.
• Arbitrary percentiles may now be expressed in the configuration.
• Percentile exposition format has changed to allow arbitrary percentiles. They are now expressed in a decimal format padded to 2 digits before the decimal. For example, the 5th percentile is now p05 and the 99.9th percentile is now p99.9.