BUG: Bug in multi-axis indexing using .loc on non-unique indices (GH6504)
Merge pull request #6506 from jreback/dup_loc

BUG: Bug in multi-axis indexing using .loc on non-unique indices (GH6504)
ENH: add method='dense' to rank
BUG: Changes types used in packing structs

Started work on correcting incorrect types in struct unpacking
Corrected incorrect data type conversion between pandas and Stata

Remove unnecessary, potentially precision degrading cast to Series when writing data
Added function to cast columns from NumPy data types to Stata data types
Corrected tests for correct Stata datatypes
Fixed formatting in comparison after casting
Added docstring for new function and warning class
BUG: Fixes and tests for extreme values in all data types

The extreme values of float and double (Stata, pandas eqiv: float 32 and
float64) were not correct.  This resulted in incorrect truncation. The
handling of missing values have been improved and code to convert missing
values in any format has been added.  The improvement differentiated between
valid ranges for data and missing values.

Additional issues were found when handling missing Dates, where missing Dates
(NaT) were converted to non-missing dates when written.

A test has been added for extreme numeric values as well as missing values.
BUG: Fixes and tests for extreme values in all data types

The extreme values of float and double (Stata, pandas eqiv: float 32 and
float64) were not correct.  This resulted in incorrect truncation. The
handling of missing values have been improved and code to convert missing
values in any format has been added.  The improvement differentiated between
valid ranges for data and missing values.

Additional issues were found when handling missing Dates, where missing Dates
(NaT) were converted to non-missing dates when written.

A test has been added for extreme numeric values as well as missing values.
BUG: Fixes and tests for extreme values in all data types

The extreme values of float and double (Stata, pandas eqiv: float 32 and
float64) were not correct.  This resulted in incorrect truncation. The
handling of missing values have been improved and code to convert missing
values in any format has been added.  The improvement differentiated between
valid ranges for data and missing values.

Additional issues were found when handling missing Dates, where missing Dates
(NaT) were converted to non-missing dates when written.

A test has been added for extreme numeric values as well as missing values.
Disabled the big endian skips
Fixed legacy date issue with format 114 files
Added test for 114 files
Added format 114 (Stata 9/10/11) data file
Add test for Stata data with file format 114
Added additional data files for testing alternative Stata file formats
Added expected result to test
Renamed Stata data files to include file format
Fixed final PEP8 issues in test_stata