Backbone is used by calling network request methods on individual references. Although this makes it much easier to implement features such as caching, it also means that an operation such as "list all users' name"'" takes `n+1` requests if the cache is empty. This merge request introduces the method `Backbone.batchRequests` and the class `Cache.Batching`. When using this layer, requests for the same provider started at the same time are batched together. Only a single network call per batch is necessary. Closes #8 See merge request opensavvy/pedestal!8