py-patsy: updated 0.5.0

v0.5.0:
* Dropped support for Python 2.6 and 3.3.
* Update to keep up with pandas API changes
* More consistent handling of degenerate linear constraints in
  :meth:DesignInfo.linear_constraint
* Fix a crash in DesignMatrix.__repr__ when shape[0] == 0

(adam)