Release 0.2.0

Features

• New: We created lambda_runtime_core crate that implements the runtime's main loop and supports handlers that accept and return Vec<u8>. (#53)
• New: The primary lambda_runtime crate is a wrapper on top of the lambda_runtime_core handler (#53).
• New: The lambda_http crate, which enables support for API Gateway or ALB requests, treating them as Request structs from the http crate (#18 by @softprops).
• 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).