Use entrez for journal lookup

[vincerubinetti]

Scimago rankings list journals by their full names, but iCite returns journals by their abbreviated/short/id names.

Previously I was using Scimago's search, which doesn't reliably return the right journal as the first result. #16 changes this to scrape the NLM catalog search instead, which works fine, but it'd be more appropriate to use an actual API since once exists.

I can do this query (with TA) to get a journal's (pubmed?) id, then this query to get its fulljournalname, which should hopefully be the same as the NLM catalog search shows (which so far seems to match what Scimago has as the title).

Scimago rankings aren't a high priority, but I'm guessing we'll eventually need to use the entrez tools to look something up, so I might as well create some type definitions and api funcs for them.