Move md-cell display logic to css
remove useless comment
update to warnings
Update path.py

change str formatting to repr representation.
Handle 'deletable' cell metadata
Add tests for undeletable cells
Make cell be undeletable ONLY when metadata is explicitly false
Fix tests
Allow timeout and click callback
Add documentation to NotificationWidget methods
Add documentation to notification area
Small changes to notification widget
Add tests for notification area and widgets
Properly mock winreg functions for test

Fixes a lot of test failures on Python 3.4 on Windows, caused by
importlib trying to use our mocked out winreg functions when
reload(path) was called.
Make Widget.views be an object indexed by view id
Clarify stickiness of warning/danger notifications
put back null gui hook for osx

`--gui osx` doesn't make sense on its own,
but it's called by `--matplotlib osx`,
which does.
Fixed off by one error in get_prev_cell

Not sure why this was a TODO. Maybe `find_cell_index()` returned zero at one time, but in the browsers I tested, it always returns null if not found.
add MultiKernelManager.default_kernel_name configurable

sets the kernel name to use, if unspecified
allow kernel_name to be undefined in requests

fallback to KM.default_kernel_name in that case