Don't fail if missing-rules:* scripts fail
Don't fail if missing-rules:* scripts fail

`eslint-find-rules` currently reports deprecated rules as missing, and
so exits with a non-zero exit code.  This behavior makes the current
`missing-rules` npm script essentially useless.

For now, this adds the `—no-error` flag to all of the calls to
eslint-find-rules so that they always exit cleanly.

Once https://github.com/sarbbottam/eslint-find-rules/issues/172 gets
done, we should be able to revert this change.  We could even then
include the `missing-rules` task in our CI validation suite, failing
the build if there are missing rules.

CodingZeal/eslint-config-zeal