[pyos][design] accepting strings as inputs, especially in the interactive mode

[giovana-morais]

part of: pyOpenSci/software-submission#267 (comment)

i think considering the use case of this library, i find it a bit odd that the incomplete references are always in .txt or .bib files. when the documentation showcases examples of a single reference that needs to be corrected, it still need to be inside a .txt file.

i think it would be a great API addition to be able to provide a string directly. in my opinion, this would be especially true in the interactive mode.
using, again, the "attention is all you need" example:

onecite process "attention is all you need, nips 2017" --interactive

should be the same as doing

echo "attention is all you need, nips 2017" > references.txt
onecite process references.txt --interactive