* added doc for parameter 'coerce_float' in io.sql.read_frame
adjusted the indentation of doc of io.sql.read_frame
fixed conflict in sql.py
ENH col_level argument to melt
ENH MultiIndex columns with melt
ENH add drop_na argument to pivot_table
CLN make cartesian product faster
DOC: Update excel read dependency on ``xlrd``

Since 98f65b19f918b825ae6cb1001cd8e91f45377cc7,
``xlrd`` handles reading both ``.xls`` and ``.xlsx`` Excel Files.
DOC: Update docstrings to reflect benefit from resolving #4131

1bd8f57d68686f268922a1e230c5a8f2e4e3cc9d resolves #4131 without
updating docstrings in relevant functions.  No way to know that keep_default_na
and verbose are valid keyword arguments without inspecting the parsers.py code
and documentation
BLD: add requirements files and update install.sh

This commit adds 5 requirements files: one for each Travis build. The
corresponding sections in ci/install.sh are also removed in favor of these
files.

This allows pandas to have more fine-grained control over versions of
hard and soft deps when using travis.
Merge pull request #4153 from cpcloud/req-files

ENH: add correct versions of numpy installs
BUG: fix failing usage of self.assertRaisesRegexp for python 2.6
BLD: use the wheel url for scikits timeseries
RLS: first release candidate for v0.12.0
BUG/TST: wrong parsing of microseconds with format arg (#4152)
Merge pull request #4166 from jorisvandenbossche/bug-microsecond-parsing

BUG: wrong parsing of microseconds with format arg (#4152)
DOC: minor io/whatsnew doc edits
TST: to_datetime format fixes

CLN/TST: to_datetime cleanup

TST: tests for dayfirst=True
Merge pull request #4168 from cpcloud/sktimeseries-dl-fix

BLD: use the wheel url for scikits timeseries
Merge pull request #4167 from jreback/dt_format

TST: to_datetime format tests