ENH: Medcouple for robust skewness estimation
ENH: Function allowing other functions to be applied using only 1d
    at a time
ENH: Robust Skewness from Kim and White
ENH: Robust Kurtosis from Kim and White
ENH: Helper functions for quantile.  Different from numpy.
ENH: Tests for medcouple
BUG: Made use of np.apply_along_axis and replaced custom version
General improvements to robust skewness and kurtosis
ENH: Generalized other texts to work along axis for standards
Simplified code to remove new weighted quantile function, instead
    use np.percentile
Removed incorrect test file in tools/tests/test_statstools.py
Added tests for multi-axis functions in stattools
Clean-up and documentation for robust skewness and kurtosis measures
Cleaned-up stattools
Added docstring for those missing
Added test for robust kurtosis
Fixed defect where ties were not handled correctly by medcouple
Reverted space additions around ** operator
Removed unnecessary float powers
100% test coverage

Conflicts:
	statsmodels/stats/tests/test_statstools.py
Revert auto-spacing
ENH: Added flag to select excess or not
Allows raw values to be returned when excess=False

Conflicts:
	statsmodels/stats/stattools.py
Added test for excess=False case

Conflicts:
	statsmodels/stats/tests/test_statstools.py
Vectorized np.percentil use
Switched to vectorized use of np.percentile where appropriate
Cleaned up some excessively verbose code

Conflicts:
	statsmodels/stats/stattools.py
Documentation improvements and additional options
Added math to robust_kurtosis
Added math to robust_skewness
Made some of the parameters in robust_kurtosis settable
Added tests of new features

Conflicts:
	statsmodels/stats/stattools.py
Improved documentation of robust kurtosis
Separated the expected kurtotis calculation

Conflicts:
	statsmodels/stats/stattools.py
Added a release note.
Fixed rebase issues
Fixed spacing with **
Merge pull request #1234 from bashtage/medcouple

ENH: Robust skewness, kurtosis and medcouple measures