BUG: Removing a nonexistent store raises a KeyError
BUG: GH3455 Duplicate indexes with getitem will return items in the correct order

BUG: GH3457 to_csv writing duplicate columns incorrectly
Merge pull request #3447 from danielballan/remove-raises-keyerror

BUG: Removing a nonexistent store raises a KeyError (GH3346) - thansk!
Merge pull request #3459 from jreback/GH3455

BUG: GH3455 Duplicate indexes with getitem will return items in the correct order
TST: to_csv respects cols= reordering GH3454/7
BUG: to_csv handles cols= reordering,dupe cols GH3454/7
DOC: update RELEASE.rst

PTF