no-restricted-paths: `deep` mode

In addition to checking resolved imported paths for restrictions, could also deeply traverse the imports of imports and report if there is any deep module dependency on a restricted path.

Would not be necessary if you are linting all the dependencies together, since the root module would report the original import, but could be useful in a context like Sublime where a deep relationship might have snuck in elsewhere (like a `git pull`).

Would also be useful if all the intermediate dependencies are not being linted. This would be able to traverse imported `node_modules` if ES6 was available (e.g. via `jsnext:main`).

@lo1tuma: thoughts?

Start by locating the no-restricted-paths rule entry point and its existing tests. Review how resolved imported paths are checked, then define the traversal behavior and reporting expectations for transitive dependencies, including imported node_modules; done means deep restricted-path dependencies are reported without requiring every intermediate dependency to be linted.

Written by the indexing model from the issue text.