Handle tsconfig.json errors without using JSON.stringify

[mertdeg2]

JSON.stringify fails in some cases because its fails to convert circular structure to string

PR checklist

• Addresses an existing issue: #0000
• New feature, bugfix, or enhancement
  • Includes tests
• Documentation update

Overview of change:

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

CHANGELOG.md entry:

[palantirtech]

Thanks for your interest in palantir/tslint, @mertdeg2! 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.

[suchanlee]

what issue does this fix?

[mertdeg2]

Without this change, TSLint chokes while trying to report failures. Some failures contain circular structures. And JSON.stringify can’t handle those

[giladgray]

yeah i've seen this used before. nice.