BUG: "converters" in read_excel with missing data
docs fix (?)
Revert "Fix unrecognized 'Z' UTC designator"

This reverts commit 0e02d5f275234b11d699ce13aa4da4f3624d0f7d.

Conflicts:
	doc/source/whatsnew/v0.15.2.txt
DOC: Added get_group subsection
Merge pull request #8811 from MatthewGilbert/master

DOC: Added get_group() example to grouby.html
Merge pull request #8548 from iosonofabio/excel_dtype

BUG: inconsistent and undocumented option "converters" to read_excel
Merge remote-tracking branch 'upstream/master'