• Disabled unused variable warnings for variables that begin with _

fix: Revert new errors warnings, place chai rules in +chai

chore: Added chai and promise eslint plugins.

Updated peer dependencies babel-eslint to 9.0.0.

Updated semver and eslint to latest minor/patch updates.

Republish of v2.1.0.

Fixed package-lock.json.

Republish of v2.1.2.

Version bump due to botched 2.1.1 publish.

Revert v2.1.0 changes.

Removed deprecated "experimentalObjectRestSpread" flag in favor of bumping the ecmaVersion to 9.

Updated npm deps include eslint to 5.3.0.