Pagination

[tanner0101]

Implements pagination helpers using new APIs from vapor/fluent-kit#130.

struct TodoController {
    func index(req: Request) throws -> EventLoopFuture<Page<Todo>> {
        Todo.query(on: req.db).paginate(for: req)
    }
}

[tanner0101]

These changes are now available in 4.0.0-beta.2.1