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.
