IPython Notebooks not robust against client failures

[tmbdev]

Right now, it is possible to lose arbitrary amounts of work when working in IPython Notebooks when the client or the server crash for some reason (machine shutdown, power loss, bug in Python code, etc.).

Many use cases (lab notes, software development, classroom use, etc.) require that IPython Notebooks be robust against such failures; that is, I should be able to pull the power plug on my machine and not lose more than a minute of work or so even if I never save.

Most other modern apps (Google Docs, OpenOffice, Eclipse, Emacs, etc.) have that level of robustness, which compounds the problem with IPython Notebooks because people simply aren't used to having to save frequently anymore. Furthermore, since manual saving overwrites the last version (which the user may care about having around), frequent manual saving is often not even acceptable.

[minrk]

closing as duplicate of #1378