Indicate error/warn status and options for missing rules

[brettz9]

This is indeed an awesome tool, thank you!

For rules that are missing, it would be handy to know if they had been declared as errors, warnings, etc., along with the options they were set with (preferably converted to JSON for the --json option).

(Btw, in answer to the question raised on your README to-dos "How to get the default?", regarding how to canonicalize to compare explicit defaults within implicit defaults in an equivalent manner, you can get at this if the rule indicates its defaults through schema. E.g., for valid-jsdoc, https://github.com/eslint/eslint/blob/master/lib/rules/valid-jsdoc.js#L28-L46 , requireReturn is indicated with a default of true.)