Don't try to open an empty response, and don't try to rename to the same name.

Fix other weird behaviors.

Keep track of whether or not a notebook has been persisted.
This lets us explicitly name it the first time it's saved.
Also fixed where it would try to rename EVERY notebook at once.

Have to use the new name to save.

Also updated tests.

Fixes #104.
Merge pull request #123 from joneshf/ready/104

Opening/Renaming Notebooks