Add strip_from_keys option. Allow client config options and shared credentials

[jplindquist]

• Add new option to strip prefix(es) from keys as needed, similar to the vault module here
• Allow arbitrary client config options to be passed in as a hash (backwards compatible with previous default)
• Enable shared credentials file to be managed outside of the module by specifying a shared credentials file and profile to be used instead of an access key and secret key (which enables for easier credential rotation)
• Enable caching

[brendanhill]

any traction on this? would love the feature...