[WIP] Support Consul 1.4.x ACLs

[scalp42]

Related to #193, adding two new classes, Policy and Token.

• [x] Diplomat::Policy
• [x] Diplomat::Token

~This is a work in progress.~

I vaguely remember having rights on the repository 🤷‍♂

[scalp42]

Feel free to review now @pierresouchay 🇫🇷

I'm going to work on https://github.com/sous-chefs/consul/issues/520 🌤

[scalp42]

Using Consul cookbook fork as test bed.

Let me know when you can review.