v0.3.3

Fixed

• Busy spin in the metrics worker. Its select had a default: branch that called DequeueMetrics back to back, so whenever the call returned at once (SQS and database stores when empty, the memory store before its first metric, any store on error) the goroutine burned a full CPU core and, on errors, flooded the log. It now polls on a timer: after an empty or failed call it waits 1s (metricsIdleWait), after a delivered metric it polls again immediately to drain. Shutdown and new metrics still interrupt the wait. Regression tests: TestMetricsWorkerDoesNotSpinWhenIdle, TestMetricsWorkerDeliversMetric.
• TestVersion no longer hard-codes a version string, which had it failing since 0.3.2.