ENH ohlc resample for DataFrame
CLN refactor with _apply_to_column_groupbys
INT: add TimeDeltaBlock support in internals

ENH: GH3371 support timedelta fillna
BUG/ENH: add bfill/ffill support for datetime64[ns]
BUG: read_fwf: incorrect error message with no colspecs or widths
Merge pull request #4774 from jtratner/fix_fwf_error_msg

BUG: read_fwf: incorrect error message with no colspecs or widths
API: provide automatic dtype conversions on _reduce operations
API: exclude non-numerics if mixed types in _reduce operations

BUG: timedelta fixes

CLN: small cleaning in nanops.py

BUG: allow _reduce to call .apply for certain operations when the who block fails
     via a reduce exception
Merge pull request #4684 from jreback/timedelta_fill

ENH: GH3371 support timedelta fillna
DOC: updated release.rst to conform headings
BLD: make test_perf.sh work on OSX too
TST: (GH4550) where with a dup index in Series
BUG: (GH4548) inplace updating of a duplicate Series with a boolean aligning incorrectly
Merge pull request #4779 from jreback/dups_ops

TST/BUG: duplicate indexing ops with a Series using where and inplace add buggy (GH4550/GH4548)
BUG: Fix read_fwf with compressed files.

`gzip` and `bz2` both now return `bytes` rather than `str` in Python 3,
so need to check for bytes and decode as necessary.
Use passed encoding to decode bytes
Merge pull request #4784 from jtratner/fix-read-fwf-with-compression

BUG: Fix read_fwf with compressed files.
ENH: Add axis and level keywords to where, so that the other argument
     can now be an alignable pandas object.
Merge pull request #4740 from hayd/ohlc_dataframe

ENH ohlc resample for DataFrame
Merge pull request #4781 from jreback/where

ENH: Add axis and level keywords to where, so that the other argument can now be an alignable pandas object.
CLN: add Timestamp reference in core/common.py