ENH: Make ExcelWriter & ExcelFile contextmanagers

both can be used in with statements now. Makes it easier to use with
multiple writers, etc.

Plus touch up the docs on writers and such.
Added to docstrings in factorize function
DOC: add HTML bad-request cookbook example
Merge pull request #4933 from jtratner/make-ExcelWriter-contextmanager

ENH: Make ExcelWriter & ExcelFile contextmanagers
BUG: Fixed a bug with setting invalid or out-of-range values in indexing
     enlargement scenarios (GH4940)
Merge pull request #4943 from jreback/e_dtype

BUG: Fixed a bug with setting invalid or out-of-range values in indexing enlargement scenarios (GH4940)
CLN: removed Panel.fillna, replacing within core/generic.py/fillna
Merge pull request #4951 from jreback/fillna

CLN: removed Panel.fillna, replacing within core/generic.py/fillna
BUG: Conflict between thousands sep and date parser.

Fixes issue where thousands separator could conflict with date
parsing.

This is only fixed in the C parser.

Closes issue #4678
BUG: fix issue #4678 for Python parser
TST: Tests for fillna on empty Series (GH4346), thanks @immerrr
BUG: fix incorrect TypeError raise

TypeError was being raised when a ValueError was raised because the
ValueError's message wasn't being converted to a string.
Merge pull request #4957 from cpcloud/hdfstore-append-error-fix

BUG: fix incorrect TypeError raise
BUG: Fix copy s.t. it always copies index/columns.

Only copies index/columns with `deep=True` on `BlockManager`. Plus some
tests...yay! Change copy to make views of indices.

Requires changing groupby to check whether indices are identical, rather
than comparing with `is`. Plus add tests for name checks through
everything. Also, fixes tests to use `is_()` rather than `is`

CLN: Change groupby to use 'is_' instead
ENH: enable deep copy for sparse Series/Panel
CLN: PEP8 tests/test_index.py and core/index
Merge pull request #4830 from jtratner/copy-index-and-columns

BUG: Fix copy s.t. it always copies index/columns.
DOC: remote_data.rst: Fama/French punctuation
Merge pull request #4965 from westurner/patch-1

DOC: remote_data.rst: Fama/French punctuation
BUG: fix skiprows option for python parser in read_csv