PERF: perf improvements in timedelta conversions from integer dtypes
DOC: documented that .apply(func) executes func twice on the first time

Related issues are #2656, #2936 and #6753.
Merge pull request #6756 from anton-d/master

DOC: documented that .apply(func) executes func twice on the first time
Merge pull request #6754 from jreback/timedelta_perf

PERF: perf improvements in timedelta conversions from integer dtypes
DOC: correct alignment of GH6756
BUG: Series.iteritems should be lazy
ENH: Panel.shift now uses NDFrame.shift.
PRF: Adding Panels.shift test

DOC: Panel.shift no longer drops periods.
Merge pull request #6761 from TomAugspurger/lazy-iteritems

BUG: Series.iteritems should be lazy
Merge branch 'general-shift-4867-panel' of https://github.com/dalejung/pandas into dalejung-general-shift-4867-panel

Conflicts:
	doc/source/release.rst
	doc/source/v0.14.0.txt
PRF: Optimize 2d take operations.
Use memory views