Display prompt in the notebook correctly
Display prompts in html nbconvert output
Display prompt numbers correctly in latex output
Add regression tests for live notebook
Add regression tests for html nbconvert
Also handle case where prompt number is undefined
Add regression test for latex color prompts
Handle case where prompt number is not defined in latex templates
Add a few more edge cases for prompt numbers in nbconvert
Have prompt number tests use a special prompt number notebook
Revert changes to notebook2.ipynb
Make prompt numbers notebook more specific
Merge pull request #6706 from jhamrick/display-prompt-numbers

Correctly display prompt numbers that are 'None'
copy nbformat.v3 to v4
update v4 schema

use jsonschema refs, no need for jsonpointer
update v4 schema mime-type expression

fixes inappropriate JSON match
source is required in all cells
raise ValidationError in v4 validate

also only load the schema once and store it in a module global
first complete pass on v4

tests passing, notebooks validating
Use Draft4 JSON Schema for v4