Update `curry` and `reduceby` to match those in toolz

Matches curry changes from pytoolz/toolz#170
Matches reduceby changes from pytoolz/toolz#184
Use op-code constants `Py_EQ` and `Py_NE` for rich comparisons
Merge pull request #37 from eriknw/update_curry_reduceby

Update `curry` and `reduceby` to match those in toolz