Add mangle_dupe_cols option to read_csv/table GH3468
DOC: add RELEASE.rst note anticipating breaking change in 0.12.0
Merge pull request #3511 from y-p/PR_mangle_dupe_cols_option

ENH: add mode.mangle_dupe_cols option GH3468
Added failing test case for union of two timezone-aware indexes with month end frequencies.

Signed-off-by: Kevin Stone <kevinastone@gmail.com>
Included timezone information when applying month-end offset to ensure timezone information is preserved on index unions.

Signed-off-by: Kevin Stone <kevinastone@gmail.com>
DOC: update RELEASE.rst
DOC: Fix header
Merge pull request #3530 from jseabold/docs-cleanup

DOC: Fix header