Update setup.py for release v3.1.2 (#1265)
Update setup.py for release v3.1.2 (#1265)

Release Notes for 3.1.1 and 3.1.2
- Added support for adding an in-memory object (such as a pandas.DataFrame) to a package via package.set()
- Fix to work with pyarrow 0.15.0
- Performance improvements for list_packages and delete_package
- Added list_package_versions function
quiltdata/quilt-compiler,quiltdata/quilt-compiler,quiltdata/quilt,quiltdata/quilt,quiltdata/quilt,quiltdata/quilt,quiltdata/quilt-compiler,quiltdata/quilt-compiler,quiltdata/quilt