`pre`, `code` tags already set the font-family in these contexts.
Setting it again in the surrounding context is redundant,
and causes inconsistency when embedding notebooks in HTML
(e.g. nbviewer).
This was inspired by PR #4105.
* JavaScript output no longer requires calling container.show()
* Added output_javascript CSS class that has zero height when
empty.
* JavaScript error messages are properly indented with the prompt
area.
MinRK
Jonathan Frederic
Brian E. Granger
Matthias BUSSONNIER