Merge pull request #1480 from minrk/npmagic Fix %notebook magic, etc. nbformat unicode tests and fixes. * json.writes always gives unicode, so that `current.writes` can be trusted to give the same interface * setup base TestCase for nbformat tests, to consolidate code, and better test both file formats * add tests for reading/writing to files * allow `name` as kwarg to new_notebook to avoid unnecessary breakage of previous API. * remove fallback to xml, which would hide corrupt notebook files behind a nonsensical 'xml unsupported' message. Closes #1545, #1487.