Major version bump dependencies

[bjankord]

Issue Description

A few of the dependencies this package relies on have released major version bumps.
We should work on updating and testing these new releases.

Issue Type

• New Feature
• Enhancement
• Bug
• Other

Expected Behavior

eslint-config-terra uses the most stable and update to date dependencies.

[bjankord]

eslint

• eslint v6 has been released: https://github.com/eslint/eslint/releases/tag/v6.0.0
• We are waiting on eslint-config-airbnb to update to add support for eslint v6: eslint v6 support airbnb/javascript#2036

eslint-plugin-compat

• eslint-plugin-compat v3 has been released: https://github.com/amilajack/eslint-plugin-compat/releases
• related PR to update to support eslint@6: bump eslint peerDep to eslint@6 amilajack/eslint-plugin-compat#243

We may want to wait for other eslint packages we use to add support for eslint v6 before we do this upgrade.