Expect list resource to use singular name of model

[mdnorman]

The docs say to define models queries like so:

type Query {
  messages: [Message]
  message(id: ID): Message
}

However, this creates resources like so:

GET /messages
GET /message/:id

For a standard rest interface, I would expect the resources would be:

GET /message
GET /message/:id

That way the list and single value have the same resource path.