BUG: unwanted conversions of timedelta dtypes when in a mixed datetimelike frame (GH7778)
TST: tests for internals/as_matrix() for all dtypes (including categoricals)
Merge pull request #7779 from jreback/td

BUG: unwanted conversions of timedelta dtypes when in a mixed datetimelike frame (GH7778)
Docs: Categorical docs fixups.
Merge pull request #7783 from lexual/docs_categorical_tidyup

Docs: Categorical docs fixups.
BUG: Fix for multiple ints as levels in DataFrame.stack()

BUG: Fix for multiple ints as levels in DataFrame.stack()

If passed levels match level names, use them directly

Add test cases for multiple stacking

Add check for out of range negative level num in _get_level_number()

Use _get_level_number() to do validation and conversion

Explain why level list isn't iterated over directly

Raise exception on fall-through case

Add test cases for raising exceptions

Use _get_level_number() to convert and validate negative levels

Add changes to release notes

Fix Python 2.6 build issue: use assertRaisesRegexp from testing module

Add tests for out of bounds level numbers

Move API change note to correct section

Add blank line after if/elifs