v0.2.0

• APIAddon.Period (daily or monthly), APIAddon.RPM and
  APIUsage.DailyRequestsUsed from the usage endpoint.
• APIUsage.Allowance returns the limit, its period and the usage counted
  against it: requests today on a daily allowance, credits this month on a
  monthly one. It reports false for no, unknown or mixed periods instead of
  guessing.
• CreditsPerMonth is deprecated: an allowance may be daily.

v0.1.0

Initial public release.

• Metric time series: scalar (GetTimeSeries), object (GetObjectTimeSeries),
  bulk (GetBulkMetric) and custom shapes (GetMetric). Point-in-time metrics
  expose ComputedAt; bulk entries keep every selector in Params.
• Asset and metric metadata, metric lag statistics, and lists of metric tags,
  asset tags, categories, blockchains, exchanges, networks and miners.
• API credit usage (GetAPIUsage).
• CSV downloads of a metric to an io.Writer (GetMetricCSV).
• Generic Get and Raw for endpoints without a dedicated method.
• Authentication with an API key (header or query) or an existing OAuth access
  token, fixed or from a TokenSource; a TokenRefresher can replace a token
  the API rejected with 401.
• Context cancellation, a per-attempt timeout and retries with jittered
  backoff that honour Retry-After and x-rate-limit-reset, with the wait
  exposed as APIError.RetryAfter.
• Optional response size limit (WithMaxResponseBytes).
• Typed errors with credentials redacted from messages; redirects are never
  followed.
• No dependencies outside the standard library.