Dynamically create and remove upstreams?

Hi,

First of all, this is a super awesome project & exactly what I've been looking for in the last few weeks - it was a difficult one to find!

At the moment, as far as I can see, dshackle has support for a static list of upstreams as defined in a yaml file, but there's no way to remove upstreams or add them depending on application load/etc. Would such a feature be beneficial to the project?

If so, I'd be quite interested in implementing.