BUG: tzinfo lost when concatenating multiindex arrays
BUG: Easter works incorrectly in negative offsets
BUG: CustomBusinessDay apply raises NameError when np.datetime64 is passed
Merge pull request #7195 from sinhrks/easter

BUG: Easter works incorrectly in negative offsets
BUG: Bug in broadcasting with .div, integer dtypes and divide-by-zero (GH7325)
Merge pull request #7328 from jreback/div_error

BUG: Bug in broadcasting with .div, integer dtypes and divide-by-zero (GH7325)
Merge branch 'custombd' of https://github.com/sinhrks/pandas into sinhrks-custombd

Conflicts:
	doc/source/v0.14.1.txt
Merge branch 'concattz' of https://github.com/sinhrks/pandas into sinhrks-concattz

Conflicts:
	doc/source/v0.14.1.txt
BUG StringMethods on empty series (GH7242)

- all StringMethods are tested and work on empty seires
- moreover extract always returns dtype==object, even when no match is
  found
implement additional tests for groupby apply methods
simplify groupby's std method
add sem to nanops
add sem to aggregate methods
add sem to groupby
add sem to docs