cleave graph and package metadata

[CJ-Wright]

We seem to be getting a lot of thrashing of the graph file in cf-graph-countyfair. I think some of this could be avoided by having the graph only contain the relationships among packages and links (via lazyJSON) to the actual feedstock metadata.

This would then help with #34 since the webservice could write to each package's metadata file without fear of having git clashes. Then the bot would not need to update the feedstocks itself, all it would need to do is rebuild the graph so that any new relationships are added to the structure. This might also help with the merging of countyfair and libcfgraph.

[CJ-Wright]

This may require all of our nodes to have a top level key of payload so we can load in the lazyjson object.