Make middleware stack enumerable and add docs (#1191)
Make middleware stack enumerable and add docs (#1191)

* Include Enumberable into Hanami::Slice::Routing::Middleware::Stack

We were already defining the `#each` method to delegate to the
underlying data structure. We go now all the way down to be able to use
any Enumerable method.

* Add some docs to Hanami::Slice::Routing::Middleware::Stack
hanami/hanami,hanami/hanami