4.0.0

• upgrade prom-client to ~11.1.1
• upgrade url-value-parser to ^2.0.0
• add option urlValueParser

3.3.0

• added an option promClient: {collectDefaultMetrics: {timeout: ...}}
• upgrade prom-client to ~10.2.2 (switch to semver "approximately")

3.0.0

• upgrade dependencies, most notably prom-client to 9.0.0
• switch to koa v2 in koa unittest
• only node v6 or higher is supported (stop supporting node v4 and v5)
• switch to npm5 and use package-lock.json
• options added: includeStatusCode, formatStatusCode

2.2.0

deprecate excludeRoutes, use req.originalUrl instead of req.path