Override from_formula so that extra array args can be passed by name
Test maintenance
BLD: Include README in sdist
BLD: Check for dependencies unconditionally. Closes #1897.
Merge pull request #2007 from jseabold/fix-build-issues

BLD: Fix build issues
Merge pull request #1954 from kshedden/phreg_formula

ENH: PHReg formula improvements
FIXUP/WIP: Refactor to use generic data handling
ENH: Allow more general param_names in data handling
ENH: Allow attachment of generic names.
ENH: Refactor to allow wrappers to work.
ENH: Handle the generic 2d case.
ENH: Wrap 2d attributes
REF: Return DataFrame instead of dict.
TST: Fix tests for refactor
STY: Rename attributes
DOC: Update release notes example
ENH: Let t_test use param_names for better or worse.
REF: Keep bse
REF: likeval -> llf
ENH: Define df_resid so t_test works.