Update grunt-eslint to version 18.1.0 🚀

[greenkeeperio-bot]

Hello :wave:

:rocket::rocket::rocket:

grunt-eslint just published its new version 18.1.0, which is not covered by your current version range.

If this pull request passes your tests you can publish your software with the latest version of grunt-eslint – otherwise use this branch to work on adaptions and fixes.

Happy fixing and merging :palm_tree:

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The new version differs by 3 commits .

• dcb77b9 18.1.0
• 3dce1da don't error out when there are no files to lint
• 4aa763b meta tweaks

See the full diff.

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