no issue
- returns the promise/result from `loadNextPage` so that it's return value can be utilised in closure actions
- sets the `isLoading` property in `loadFirstPage` to match `loadNextPage` behaviour
- reset the `isLoading` property even if the request fails
- adds a `didReceivePaginationMeta` hook so that consumers of the mixin can use the metadata values without having to rely on observers
- eg. pulling the `total` into a separate property that can be manipulated when items are added/removed but still reset to the sever's total value the next time a page is loaded
- renames the `pagination-route` mixin to simply `pagination` as it's not tied to routes and works equally well in other objects that need to paginate an API resource
