long output redirected to file

[jasongrout]

In the sage notebook, if there is very long output, it is redirected to a file and the display is just updated with the beginning and end of the file. This would be a nice feature to have, but probably not crucial for the first release, since people will mainly be using this for smaller things, I imagine.

[jasongrout]

We could do this from the output handlers...they could keep track of the amount of output and then automatically redirect to a file if needed. At the end of the session, a file message could be sent.