factor valid cell index logic
refactor cellc
Updating notebook compat docs.
abstract, cleanup and document

Separate the methods that actually insert dom element for easier
testing.

Cleanup, and order methods more logically

add "docstring"
Removing old dev docs.  All of this has been moved to GH wiki.
Adding link from Sphinx dev docs to GH wiki Dev: Index.
simplify logic
remove unused/not working function
move CM IPython theme out of codemirror folder
fix count when testing composite error output
don't color engine tracebacks in tests
py3: assign e so it survives outside the scope
added assert msg to extract_hist_ranges()
shows entire session history when only startsess is given
fix notebook deletion.

do not thrust what "that" is in a 3 level deep
callback
fix i/index in move up/down and == -> ===
fix one more == to ===
Changes from linting github tools
joined two message lines to one
Merge pull request #2966 from joonro/history-extract-assert-msg

Added assert msg to extract_hist_ranges()