Correctly support `>=` and `<=` for type checking

[YaraslauZhylko]

When using mypy, > and < comparison is considered valid:

from ordered_enum import OrderedEnum


class TestEnum(OrderedEnum):
   ONE = 1
   TWO = 2
   THREE = 3

if TestEnum.THREE > TestEnum.TWO:
    pass

Success: no issues found in 1 source file

But if I use >= or <=, even though it works correctly, mypy reports an error:

from ordered_enum import OrderedEnum


class TestEnum(OrderedEnum):
   ONE = 1
   TWO = 2
   THREE = 3

if TestEnum.THREE >= TestEnum.TWO:
    pass

test.py:10: error: Unsupported left operand type for >= ("TestEnum")  [operator]
Found 1 error in 1 file (checked 1 source file)

[woodruffw]

Thanks for the report @YaraslauZhylko! I'm not totally sure why that is: the APIs in this package use @functools.total_ordering, which should be handled by mypy as of https://github.com/python/mypy/pull/7831.

It's possible that the underlying problem here is that there are no annotations at all in the package, really. I can look into that later today or tomorrow.