* Implemented should_sign_header callback
* Added SigV4A to SigningAlgorithm
* Added SigV4A test
* Added debugging info to README
* Fixed memory leak from argument vectors
* Fixed memory leak of stream read buffers
* Added support for callables as option values
* Added should_sign_header support and test
* Fixed ELG type bug exposed by aws-crt-ffi change
* Updated to aws-crt-ffi v0.2.0
* Updates to stub generation
* More idiomatic fixes from PHP team
* Moved tests from src/tests -> tests, got rid of extension-only tests
* fixed up test paths, regenerated arginfo
* added credentials API, disabled FFI backend for now
* Added CredentialsTest
* Added support for specifying CMAKE_BUILD_TYPE on the command line
* Added support for AwsCredentials and StaticCredentialsProvider