New: The lambda_runtime_errors crate introduces the LambdaErrorExt trait that enables the ability to specify custom errorType values for the Lambda Runtime API. The change also includes a companion derive crate that makes it easy to automatically generate LambdaErrorExt implementations for crate-local error types (#63).
Fix: Handlers can now return any error type (#54).
Fix: Support for closures as handlers (#19 by @srijs).
Fix: Multiple bug fixes and performance improvements (thanks @Sh4rK).