Add esSpecCompliant: true to recommended trailing-comma config

[bschlenk]

PR checklist

• Addresses an existing issue: tsc & trailing-comma clash with spread operator #3960
• New feature, bugfix, or enhancement
  • Includes tests
• Documentation update

Overview of change:

TypeScript 2.9 enforces no trailing comma after rest/spread, so this
change adds esSpecCompliant: true to trailing-comma in the
tslint:recommended config.

Is there anything you'd like reviewers to focus on?

CHANGELOG.md entry:

[palantirtech]

Thanks for your interest in palantir/tslint, @bschlenk! Before we can accept your pull request, you need to sign our contributor license agreement - just visit https://cla.palantir.com/ and follow the instructions. Once you sign, I'll automatically update this pull request.

[johnwiseheart]

Thanks for your contribution!