allow discojuice to have an empty set of feeds and inline injection of entities

[Chris Phillips]

For full description of problem, see groups thread of:

https://groups.google.com/forum/#!topic/discojuice/_nTEUBarsmQ

After a lot of testing, it appears that when there's a blank set of feeds (this: [""] ) the latency is huge and store.discojuice.org results in a strange response which introduces the delay.
By adding ANY feed, the delay goes away.

I think this feels like an unhandled condition an unhandled condition that should be handled so a bug.

The model where there's an empty feed, but inline injection of metadata entities I think should be supported and not result in a round trip to hit store.discojuice.org

I've created this in the discojuice github issues section for resolution/response.

More than happy to admit I'm not using it right though anyone can guide me to the right outcome that has good performance!

Chris.