Export commonly used parts of Cadence for easy glob imports

Example

use cadence::prelude::*;
use cadence::{StatsdClient, NopMetricSink};

let client = StatsdClient::from_sink("some.prefix", NopMetricSink);

client.count("some.counter", 1).unwrap();
client.time("some.timer", 23).unwrap();
client.gauge("some.gauge", 45).unwrap();
client.meter("some.meter", 67).unwrap();
client.histogram("some.histogram", 89).unwrap();