CLN: Add _reset_cache method to PandasObject
CLN/ENH: Make names getattr'able in core/ops +PEP8.

Now the name passed to a method can be used to get that method from the
NDFrame (previously you had things like `or_ [|]`. better to just have
them all be named exactly what they are s.t. subclasses can do
`getattr(super(self, MyClass), name)(*args, **kwargs)`.
ENH: Add usecols option to python parser.

Closes #4335

Added release note and fixed py3 compat

Updated docs for consistency
TST: Added test for Excel writers with duplicated column names.

Test for issue #5235
Merge branch 'tst_excel_duplicated_cols' of https://github.com/jmcnamara/pandas into jmcnamara-tst_excel_duplicated_cols
API: add excel kw to to_clipboard to preserve compat behavior (related GH5070)
Merge pull request #5243 from jreback/clip2

API: add excel kw to to_clipboard to preserve compat behavior (related GH5070)
add ScatterPlot class to allow df.plot(kind=scatter)
API/CLN: consolidate truncate into NDFrame (panel had a separate method)
API: truncate error if before > after is now a ValueError (rather than AssertionError)
Merge pull request #5240 from jtratner/cleanup-core_ops

CLN/ENH: Make names getattr'able in core/ops +PEP8.
Merge pull request #5238 from jtratner/add-_reset_cache-to-PandasObject

CLN: Add _reset_cache method to PandasObject
Merge pull request #5244 from jreback/truncate

API/CLN: consolidate truncate into NDFrame (panel had a separate method)
BUG: fixed issue with drop on a non-unique index with Series (GH5248)
CLN: remove reindex_like from core/frame.py (use core/generic.py version)
Merge pull request #5249 from jreback/drop_dup

BUG: fixed issue with drop on a non-unique index with Series (GH5248)
Merge branch 'scatterplot' of https://github.com/zachcp/pandas into zachcp-scatterplot
API: allow Series/Panel dropna to accept other args for compat with DataFrame (GH5233/GH5250)
DOC: core/generic/drop docs from array-like to list-like
Merge pull request #5251 from jreback/dropna

API: allow Series/Panel dropna to accept other args for compat with DataFrame (GH5233/GH5250)
Merge pull request #5252 from jreback/drop_dup2

DOC: core/generic/drop docs from array-like to list-like