NetworkManager implements Manager
NetworkManager orchestrates asynchronous fetches. By keeping track of all in-flight requests it is able to dedupe identical requests if they are made using the throttle flag.
constructor(dataExpiryLength: number = 60000, errorExpiryLength: number = 1000)
Arguments represent the default time (in miliseconds) before a resource is considered 'stale'.
Will initiate network request and then dispatch upon completion.
Marks request as complete.