MNT: Remove deprecated scikits namespace
MNT: Remove scikits from setup.py
Merge pull request #575 from jseabold/remove-scikits

MNT: Remove deprecated scikits namespace. Closes #470.
BUG: Allow exog is None for is_using_patsy
TST: Test patsy DesignMatrix with exog == None
Merge pull request #578 from statsmodels/fix-577

Fix bug with Patsy DesignMatrix. Closes #577.
BUG: Fix typo in refactor. Closes #580.
BUG: Fix another refactor victim
Revert "Merge branch 'cbrunos-bugfix'. Closes #419."

This reverts commit 3bf9b65e4f5ac2e1075ffe040530751acaf4f7a4, reversing
changes made to 7c805f39a99c986e719ba5a48d7a912b3d541dc5.
TST: clean up noise emitted when running test suite.
TST: clean up warnings generated by Stata reader test.
ENH: add kernels for density estimation to nonparametric module.
ENH: add kernel density estimators to nonparametric module.

Supports continuous, ordered and unordered data (can be mixed).
DOC: add examples for nonparametric KDE estimators (uni/multi-variate).
ENH: add nonparametric regression class to nonparametric module.
ENH: add a semi-linear regression class to the nonparametric module.
ENH: add a censored regression class to the nonparametric module.
ENH: add significance test for the functional form of a distribution to nonparametric.

Note: Not yet completely finished, nor does it have tests.
ENH: add a single index semiparametric model to the nonparametric module.

Note: not yet completely finished, nor does it have tests.
STY: clean up missing variables, some PEP8 stuff, typos and docstrings.