Add support for Access Keys

[josephwegner]

Work for this was started in #104 so you don't have to start from scratch, would like to have some docs included in a PR for it.

[luchianenco]

Can you give more information about what to do, please?
thanks

[tbarn]

Hey @luchianenco!

First, I would check out the work done in #104 since it was almost complete but the pull request was abandoned. We need to make sure all of the endpoints are implemented and docs are written for them.

You can see the endpoints that we have for Access Keys in the API reference.

Examples of other SDKs with Access Keys are Ruby and Python in pull review now. These can give you an idea of the functions that need to be created.

[luchianenco]

Done here #127, please check if I have understand everything correctly.