json.array!(@crumbs) do |crumb|
  json.extract! crumb, :id, :latitude, :longitude, :user_id, :timestamp, :message

  json.author do
    json.name crumb.user.name
  end

  json.url crumb_url(crumb, format: :json)
end

json.array!(@crumbs) do |crumb|
  json.extract! crumb, :id, :latitude, :longitude, :user_id, :timestamp, :message
  json.url crumb_url(crumb, format: :json)
end

--- 
+++ 
@@ -1,4 +1,9 @@
 json.array!(@crumbs) do |crumb|
   json.extract! crumb, :id, :latitude, :longitude, :user_id, :timestamp, :message
+
+  json.author do
+    json.name crumb.user.name
+  end
+
   json.url crumb_url(crumb, format: :json)
 end
Include author in JSON crumb response
