Update of ajv dependency to 6.0.0 with only minor semver upgrade about table

[jokeyrhyme]

see: eslint/eslint#10022

[GrayedFox]

Mmm that comment strikes at the heart of the issue but there is still a bit of confusion at that point in the discussion at where exactly this problem comes from. See this comment from the same thread. TLDR: this is in fact an issue with npm itself and can be safely ignored.

If you have having trouble with CLI builds try adding ajv to your optional dependencies, than run npm install. It's a work around - nothing inside ajv, table, or eslint will actually fail (since everything needed by the modules can be seen/found by them at runtime) - this solution really is just installing an optional module so that your CLI passes or you can get a bit more sleep at night.