TST: Test GEE with missing.
STY: Remove docstrings from tests
TST: Uncomment and fix original missing data tests
ENH: Handle missing for extra data with formulas
ENH: Workaround patsy NA handling. Closes #805.
TST: Regression test for ols formula and NA category
TST: Test that raise on NA with formula is possible
MAINT: Remove deprecated ARMA order argument
MAINT: Remove deprecated names argument.
MAINT: Remove deprecated confint argument.
MAINT: Remove from deprecated namespace
MAINT: Remove deprecated methods/attributes.
MAINT: Remove deprecated KDE class
MAINT: Change deprecated signature.
MAINT: Remove deprecated attribute.
MAINT: Silence tests
MAINT: Silence test
ENH: Allow raise on missing with formula
DOC: Add NA-handling and patsy to release notes.
Merge pull request #2035 from jseabold/remove-deprecated

MAINT: Remove deprecated code for 0.6