Since memberships can be viewed from the context of a `User` or an `Organization`, I wanted to have calls to specific memberships to be accessible by a route that is more or less agnostic about its context (ie. `/memberships/1` vs. `/organizations/1/memberships/1` or `/users/1/memberships/1`). After reading http://guides.rubyonrails.org/routing.html#shallow-nesting, I felt `shallow` was appropriate.