consider implementing cascade in .stablerc #47
Description
The bootstrapping version of .stablerc "cascaded" which means that it would flatten against the .stablerc files up the tree. This behavior was changed to an explicit extends feature.
By way of background, .stablerc was inspired by .eslintrc, which supports both features ("implicit cascade" and "explicit extends").
I was puzzled by how to control implicit extends before I read about what eslint does in this situation, which is, they have a root directive which is by default false. Setting it to true stops the cascade.
Common scenarios could benefit from this feature I think. It could also be disabled at the root, which would be controlled by a cascade directive. So instead of root: true, you'd have cascade: false in the topmost stablerc and that would tell stable not to cascade any of the files lower in the tree.