"source" table not updated with add_nodes

[nhoffman]

Entries in the csv file provided to taxit add_nodes that provide source_name and source_id do update table nodes, but does not seem to create a corresponding entry in table "source"

Also, seems like nodes.source_id needs a foreign key reference to source.id

I'm using taxit v0.5.7-65-g3963e0a

[crosenth]

Here is the code that should be updating the source table https://github.com/fhcrc/taxtastic/blob/master/taxtastic/taxonomy.py#L346-L392

Let me run some more tests to see what is actually happen.