Increase the timeout before restarting Sage in live documentation

[nthiery]

I use fairly intensively the live documentation for doing Sage demonstrations and classes. An annoying thing is that the Sage session times out after only two minutes. I see the rational, but this timeout is too short: basically, whenever I take a bit of time explaining something about an example and come back to proceed through this example, I have to reevaluate everything. Also, there is no explicit feedback stating the session timed out; it took me a while to figure out why my variables were not defined anymore.

I suggest to:

• increase the timeout to, say, 10 minutes (see patch below)
• if easy, give visual feedback about the Sage session having timed out.

diff --git a/sagenb/notebook/server_conf.py b/sagenb/notebook/server_conf.py
--- a/sagenb/notebook/server_conf.py
+++ b/sagenb/notebook/server_conf.py
@@ -13,7 +13,7 @@ from flaskext.babel import gettext, lazy
 defaults = {'word_wrap_cols':72,
             'max_history_length':250,

-            'idle_timeout':120,        # 2 minutes
+            'idle_timeout':600,        # for a live documentation worksheet: quit the compute process if it has been idle for 10 minutes
             'idle_check_interval':360,

             'save_interval':360,        # seconds

[ppurka]

Fixed by #147