A couple things...

* These docs are listed as being methods in `RSpec::Rails::Configuration`, but there is no such class.  The config methods get added to `RSpec::Configuration` so it'd be good to have them doc'd as part of that class.
* These are also the methods that are generating warnings because they are defined as singleton methods on the `RSpec.configuration` object.  This is necessary for the ones that use `add_setting` (since that's an instance method of `RSpec::Configuration`) but for the others we could just define it directly on `RSpec::Configuration`.  Alternately, maybe we can find a way to use YARD directives to doc these methods at the singleton definition site so that they don't trigger the warnings?  We can probably open a YARD issue or reach out to @lsegal for advice.