Fix Issues with FY5253 and variation=nearest w/ year end in Dec
Reordered DateOffset classes after merge
API: raise SettingWithCopy when chained assignment is detected
PERF: Use xlsxwriter by default (if available)
DOC: remove docstring of flags attribute during doc building process (#5331)
Merge pull request #5450 from jorisvandenbossche/docs-flags-remove-docstring

DOC: remove docstring of flags attribute during doc building process (#5331)
DOC: small error in cookbook (doc build warning)
Merge pull request #5454 from jorisvandenbossche/patch-1

DOC: small error in cookbook (doc build warning)
BUG: Excel writer doesn't handle "cols" option correctly

Added fix to ensure that Series associated with column
names are handled correctly even if names are duplicated
or swapped. Issue #5427
Merge pull request #5429 from jmcnamara/bug_excel_cols_option

BUG: Excel writer doesn't handle "cols" option correctly
Merge pull request #5390 from jreback/chained

API: raise/warn SettingWithCopy when chained assignment is detected
BUG: pd.to-timedelta handles missing data
Merge pull request #5438 from danielballan/to-timedelta-missing-data

BUG: pd.to_timedelta handles missing data
Merge pull request #5446 from jtratner/default-imports-for-excel-writers

PERF/ENH: Use xlsxwriter by default (and then fall back on openpyxl).
PERF: performance improvements on isnull/notnull for large pandas objects
Merge pull request #5462 from jreback/perf_isnull

PERF: performance improvements on isnull/notnull for large pandas objects
Merge pull request #5405 from cancan101/fy5253_fix

Fix Issues with FY5253 and nearest w/ year end in Dec
DatetimeIndex.normalize now accounts for nanoseconds (#5461).

datetime64(ns) uses the dts->ps which was not being set to zero in the
normalize function.
TST: Fix test case to use int64 and explicit float
Merge pull request #5469 from jtratner/series-mode-test-error

TST: Fix test case to use int64 and explicit float