Fix DataFrame.to_latex() with MultiIndex columns

Currently, the positioning of \midrule is determined by the number of index
levels, not columns levels:

	>>> print pd.DataFrame({('x', 'y'): ['a']}).to_latex()
	\begin{tabular}{ll}
	\toprule
	{} &  x \\
	\midrule
	{} &  y \\
	0 &  a \\
	\bottomrule
	\end{tabular}

The fix is simple: use the number of column levels instead of the number
of index levels.
BUG: rolling/expanding_* treamtment of center
ENH: plot functions accept multiple axes and layout kw
ENH: Add duplicated/drop_duplicates to Index
BUG: Area plot legend has incorrect color
DOC: suppress warning + fix reshape example
Merge pull request #8034 from jorisvandenbossche/doc-fixes4

DOC: suppress warning + fix reshape example
Merge pull request #8027 from sinhrks/area_legend

BUG: Area plot legend has incorrect color
Merge pull request #7979 from sinhrks/dup_idx

ENH: Add duplicated/drop_duplicates to Index
Fixing 'chunksize' parameter name typo io.rst
Merge pull request #8035 from nesanders/patch-1

DOC: Fixing 'chunksize' parameter name typo io.rst
bug fix for 7987
Fix bug when testing multiindex dtypes in assert_frame_equal and assert_series_equal
Merge pull request #8042 from artemyk/fix-assert_frame_equal-multiindex-dtypes

Fix testing multiindex dtypes in assert_frame_equal and assert_series_equal
CLN/DOC/TST: Categorical fixups (GH7768)

Categorical: preserve ints when NaN are present

  `Categorical([1, np.nan])` would end up with a single `1.` float level.
  This commit ensures that if `values` is a list of ints and contains np.nan,
  the float conversation does not take place.

Categorical: fix describe with np.nan

Categorical: ensure that one can assign np.nan

Categorical: fix assigning NaN if NaN in levels

API: change default Categorical.from_codes() to ordered=False

  In the normal constructor `ordered=True` is only assumed if the levels
  are given or the values are sortable (which is most of the cases), but
  in `from_codes(...)` we can't asssume this so the default should be
  `False`.

Categorical: add some links to Categorical in the other docs

Categorical: use s.values when calling private methods

  s.values is the underlying Categorical object, s.cat will be changed
  to only expose the API methods/properties.

Categorical: Change series.cat to only expose the API

Categorical: Fix order and na_position

Categorical: Fix comparison of Categoricals and Series|Categorical|np.array

  Categorical can only be comapred to another Categorical with the same levels
  and the same ordering or to a scalar value.

  If the Categorical has no order defined (cat.ordered == False), only equal
  (and not equal) are defined.

Categorical: Tab completition tests

Categorical: Fix for NA handling/float converting in levels

Categorical: make sure fillna gets both missing values and NA-levels

Categorical: add back labels as deprecated property

Categorical: Fix assigment to a Series(Categorical)) and remove Series.cat.codes

Categorical: declare most methods in Categorical NON-API
TST: skip test_kds_colors if too old scipy installed
Fixed incorrect datatype conversion on multi-indexes

Fixed test to use assertTrue

Simplifying tests to write and read back

Simplified multiindex test to use a roundtrip

Release notes update
Merge pull request #8022 from artemyk/sql-create-table-index-dtype-fix

Fixed incorrect datatype conversion on multi-indexes
BUG: fix HDFStore iterator to handle a where properly (GH8014)
Merge pull request #8029 from jreback/hdf_iterator

BUG: fix HDFStore iterator to handle a where properly (GH8014)