DOC: fix formatting read_csv comment kwarg explanation
DOC: ignore_na warning
Switch default colormap for scatterplot to 'Greys'

In #7780, I added colormap support to scatter, but choose to override the
default rainbow colormap (7780#issuecomment-49533995).

I'm now regreting choosing 'RdBu' as the default colormap. I think a simple
black-white colormap is a more conservative and better default choice for
coloring scatter plots -- binary colormaps really only make sense if the data
is signed. 'Greys' is also the default colormap set by the seaborn package,
and @mwaskom has done far more thinking about colormaps than I have.

If possible, I would love to get this in before 0.15 is released, so we don't
have to worry about changing how anyone's plots look.

CC @sinhrks
Merge pull request #8567 from seth-p/ignore_na_warning

DOC: ignore_na warning
Merge pull request #8566 from shoyer/fix-default-cmap

Switch default colormap for scatterplot to 'Greys'
PERF: improve perf of array_equivalent_object (GH8512)
Merge pull request #8570 from jreback/equals

PERF: improve perf of array_equivalent_object (GH8512)
ENH: Add type conversion to read_stata and StataReader

Added upcasting of numeric types which will default numeric data to either
int64 or float64.  This option has been enabled by default.

closes #8527
Merge pull request #8564 from bashtage/stata-datatype-conversion

ENH: Add type conversion to read_stata and StataReader
TST/PERF: optimize tm.makeStringIndex

* add tm.rands_array(nchars, size) function to generate string arrays

* add tm.randu_array(nchars, size) function to generate unicode arrays

* replace [rands(N) for _ in range(X)] idioms:
  - with makeStringIndex in benchmarks to maintain backward compatibility
  - with rands_array in tests to maintain 1-to-1 type correspondence
BUG: dtype query with negation bug (GH8568)
DOC: updates release and v0.15.0.txt for release
DOC: fix example of GH8512 name clash with following examples
Merge pull request #8579 from jorisvandenbossche/doc-fixes015

DOC: fix example of GH8512 name clash with following examples
RLS: 0.15.0 final
DOC: start 0.15.1 cycle for docs
DOC/REL: adapt make.py file to upload with other user than pandas
Merge pull request #8575 from immerrr/optimize-makestringindex

TST/PERF: optimize tm.makeStringIndex
ENH: Allow columns selection in read_stata

Allow columns to be selected when importing Stata data files.

Closes #7935
Merge pull request #8577 from bashtage/stata-columns

ENH: Allow columns selection in read_stata