FIx minor typos and add error handling into dx.doi.org response

I've been toying around with an idea of creating a timeline of publications read using [timeline.js](http://timeline.knightlab.com/) to give an overview of literature read lately. `cites` comes in very handy. Anyways, fixes are quite small and I'm not sure if the error handling in 9dbb823ef37d82dc32ce5d72d1acb5b286cdfb77 is a good way of doing it.