Log Message:
py-rpy: updated to 2.9.1

Release 2.9.1

Changes
-------
- Fixing issue 432 (see Section Bugs fixed below) involved removed the method
  `__reduce__` previously provided for all rpy2 objects representing R objects.

Bugs fixed
----------
- An error when installing with an unsupported R version was fixed.
- The docstring for `rinterface.endr()` was improperly stating that the function \ 
was not taking
  any argument.
- Target version of dplyr and tidyr are now 0.7.4 and 0.7.2 respectively.
- Fixed memory leak when pickling objects. Fixing the leak caused a
  slight change in the API (see Section Changes above).
- Conversion to :mod:`pandas` now handling R ordered factor.
- :mod:`jinja2` was not listed as a dependency