The rubocop linter should warn you about configuration file issues

## Information

**VIM version**

NVIM v0.3.1

Operating system

I use arch linux.

## What went wrong

A recent version of rubocop deprecated some of its options. That's on rubocop. Instead of showing me the error, ale swallowed it and stopped linting.

My .rubocop.yml had `Style/TrailingCommaInLiteral` enabled. That was deprecated and replaced with separate settings for hashes and arrays.

Ale simply stopped doing anything. I think that's the wrong behavior.

I ran rubocop manually on a file I knew to be bad and got this on stderr:
```
Error: The `Style/TrailingCommaInLiteral` cop no longer exists. Please use `Style/TrailingCommaInArrayLiteral` and/or `Style/TrailingCommaInHashLiteral` instead.
(obsolete configuration found in .rubocop.yml, please update it)
```

I'd like to see that message in vim.

## Reproducing the bug

Make a bad rubocop.yml
Make some bad ruby
Point rubocop at the bad ruby
See the error
Point ale at the bad ruby
See nothing.

### :ALEInfo