Add Node 8 standards to linter

[ace-n]

Do not merge until samples have been updated to conform to these standards.

[fhinkel]

Looks good to me. But we need to update a lot of samples first. I'd prefer if we'd use the same linting rules as the client libraries.

Also, how does this work with the functions samples that are currently tested on Node 6?

[ace-n]

• Updating samples - yep, I figured as much. 🙂I wanted to make sure we agreed on the rules before I updated any samples though.
• Copy linting rules from the client libraries - those are less restrictive than these (e.g. prefer-await-to-then isn't there, but it's part of our Node 8 upgrade process).
• functions samples - I'm following up more on this internally. I might add an exception to these (either via in-file comments, or a lower-level eslintrc.yml) until we agree on a path forward.

[fhinkel]

🎉