Refactoring Notebook.command_mode.
Removing conditionals that are not needed.
Make sure we are in command mode before we select a new cell.
nbconvert: Make sure node is atleast version 0.9.12
Cleanup
Split logic onto multiple lines.
Merge pull request #5280 from jdfreder/ff_cmurlpref

append Firefox overflow-x fix
Only check for node on first call, not on import.
fix a typo introduced by a rebased PR

caused heading cells to appear in both rendered and unrendered state
Merge pull request #5281 from minrk/rebase-typo

fix a typo introduced by a rebased PR, that was causing heading cells to be displayed in both input and rendered forms.
Switch if/else order
Merge pull request #5279 from jdfreder/checknode

nbconvert: Make sure node is atleast version 0.9.12
Remove Widget.closed attribute

Closes gh-5282
Merge pull request #5283 from takluyver/widget-del

Remove Widget.closed attribute
Don't run PYTHONSTARTUP file if a file, code or module is passed

This is in line with how Python behaves
Simplify logic
Merge pull request #5226 from bouk/fix-pythonstartup

Don't run PYTHONSTARTUP file if a file or code is passed
Merge pull request #5268 from ellisonbg/cmd-mode

Refactoring Notebook.command_mode
Make nbconvert html full output like notebook's html.

Basically makes the DOM map one to one.
I used a custom in-house HTML diffing rig - https://gist.github.com/jdfreder/9241376
Removed input div from markdown and heading cells