Basically piggy-back on this: https://github.com/thisisaaronland/go-iiif#uri
Need to figure out where to store/read Flickr API details in the config.
stub out code for issue #16
issue #16 - prove that the Flickr source stuff will; still needs conf…
…ig/API key wrangling; only unsigned requests so far
issue #16: make the source.flickr config stuff; update docs