In that implementation marty keeps track of every
remotely fetched property of a store separately within the store, so, say your store holds a GitHub user with all its repos, you get the user and its list of repos separately with two separate fetches.
If you were to do it yourself (probably a cleaner approach) you could have two stores, one for the user and one for the repos and hold an internal state for it that tells whether it has data or it's fetching it from a remote source. Your app would then be aware of that fact and you would get a "status" property in your store's state that you can now leverage within your views.
You've attempted to perform the asynchronous action APIActions#sendRequest, but it hasn't been added to a Flux instance.