Remove magic for loading templates from module names
Fix tests to use full template names
Remove duplicate traitlet definition
Drop unused traitlet imports
render custom HTML for error pages
catch pandoc failures in nbconvert handlers
add error page templates
add error css
allow notebook to start without nbconvert

catches import / key errors and turns them into proper http errors
warn on failed formatter calls
remove redundant cls alias on Windows

It's already a magic, and the duplicate alias was failing with Invalid alias.
Added --post-serve explanation into the nbconvert docs.
Fixed #4580 -- Deprecated %profile.
Improve test for nbconvert citation filter.

'import lxml' was succeeding, but 'from lxml import html' was failing.
Fix EvalFormatter test for Python 3.4

Changes to string formatting mean slicing in EvalFormatter now works.
Improve Python 3 compatibility for example scripts.
It is the serve post processor and not the way to specify it.
Remove some out of date information about pandas DataFrame reprs
Improve Python 3 compatibility in example notebooks
Rerun BackgroundJobs example NB to save in new format, plus Py 3 fixes