Add Origin Checking.
Get rid of exc_info as there isn't an exception.
Indicate Py3 vs. Py2 codepath.
Use *args, **kwargs, log.warn
Performing check only on open.
Verify that headers are set, explicitly
Name change to same_origin
s/==/is/
Handle variations of name for origin
Don't enter edit mode when changing cell type and preserve renderd.
alt+enter should always insert below
shift+enter and ctrl+enter swapped.
Fixing help strings for shift|ctrl+enter.
Fixing tests from shift and ctrl enter swap.
Ignore sys.argv for NotebookNotary in tests
Fix error message typo on web socket fail
Merge pull request #4967 from Komnomnomnom/patch-1

Fix typo in warning about web socket being closed
Merge pull request #4966 from takluyver/sign-blank-app-argv

Ignore sys.argv in NotebookNotary

when creating a BaseIPythonApplication just for its profile_dir
Merge pull request #4916 from ellisonbg/modalbehavior

Fine tuning the behavior of the modal UI

swap back shift- and ctrl-enter, to their rightful places.
Merge pull request #4845 from rgbkrk/origin_host

Add Origin checking for websockets.