Fixed pandoc version detection.
Revised pandoc version detection.
Fixed indentation error.
Fixed parse_filename.
fix loginwidget css
Add EventfulList and EventfulDict trait types.
Address review comments @takluyver
Added on_events convinience method
Use ternary operator for callback registration
kwarg on_events and hardcoded callbacks
s/this/self
Upgrade default mathjax version.

This also fixes an issue with ```from IPython.external import mathjax; mathjax.install_mathjax()``` not working properly, because of a changed version schema.
Suppress virtualenv warning messages on Windows

Suppress 'WARNING: Attempting to work in a virtualenv...' message
on Windows in bash and PowerShell.  Adapts
pip.locations.running_under_virtualenv for use in no sys.executable
symlinks case.
Apply os.path.normcase to venv detection
Add local variable for normalized virtualenv path
Merge pull request #6020 from etgalloway/bash-windows-venv-warning

Disable virtualenv warning in bash on Windows
Merge pull request #6241 from cel4/pandoc_fix

Fixed pandoc version detection.
Fixed inferring the base name.
Add tests for parse_filename.
Merge pull request #6273 from bgruening/patch-1

Upgrade default mathjax version.