Introduced InstrumentedBuilder. Introduced MetricBuilder which replaces v2's MetricsGroup.
Removed scala reporter support. Removed scala version of MetricRegistry, its replaced by InstrumentedBuilder and MetricBuilder.
Removed parameter default on Counter.+=.
Removed ++ from Histogram. Its against common Scala syntax.
Cleanup: some scaladoc updates, declared result types everywhere, removed parenthesis for getters added them for procedures, removed trailing spaces.