Test built-in rule schema validation

[mdjermanovic]

refs #14

ESLint should validate configuration for built-in rules, and throw if the configuration is invalid.

We had a regression described in eslint/eslint#13793, due to the lack of tests for this scenario.

An integration test has been added in the eslint/eslint repo (eslint/eslint#13794), but we should add some unit tests to this repository, too.

[nzakas]

@mdjermanovic do you have a plan for what to do here?

[mdjermanovic]

I'm working on this.