2.0:

- Added the @MetricMod decorator, which changes the name of metrics in
  a given context. For example, "@MetricMod('xyz.%s')" adds a prefix.

- Removed the "gauge suffix" feature. It was unnecessarily confusing.

- Timing metrics produced by "@metric", "@metricmethod", and "@Metric"
  now have a ".t" suffix by default to avoid naming conflicts.