slf4j-api dependency obtained transitively from metrics-core and updated
slf4j-simple to match metrics-core version
Merge pull request #21 from mwanji/fix_slf4j_dependency

Fixed slf4j dependencies
Updated to Metrics 3.0.1. Beware of change in MetricRegistry instance
selection: by default a new instance is created and if a system property
is set, its value is used as the name in the SharedMetricRegistries.
Merge pull request #22 from mwanji/update_to_metrics_3.0

Updated to Metrics 3.0.1.
added changes for 2.0
bumped version [skip ci]