Revert "Merge pull request #5058 from neurodebian/master"

Was mistakenly incorporated as a fix, when in reality it was a missing
skip test.

This reverts commit fd3acfdb5c0530cf78abd3c17276afc94a389d60, reversing
changes made to ec54354d8c09f0efc0811272655cb585fceadc58.
TST: Add skip test to excelwriter contextmanager
BUG: non-unique indexing in a Panel (GH4960)

TST: update Panel tests to iterate by position rather than location (for matching non-unique)
DOC: str.match should (obviously) be str.extract.
Merge pull request #5099 from danielballan/minor-doc-edit-extract

DOC: str.match should (obviously) be str.extract.
ENH: add functional (but pretty slow) json_normalize function for flattening nested records per #1067
DOC: io/v0.13/release notes
CLN: py3 updates
Merge pull request #4007 from pydata/PR_json-normalize-proto

Basic JSON normalization/flattening
Merge pull request #5097 from jreback/panel_dup

BUG: non-unique indexing in a Panel (GH4960)
Merge pull request #5095 from jtratner/add-skip-test-excel

TST: Add skip test to excelwriter contextmanager
CLN/TST: Mark areas that need to be improved throughout.

* Add TODOs to places that are clearly not tested (b/c they had undefined names) and fix the undefined names
* Add TODOs to unused names.
restore orig_header for now