v0.1.0

API issubtype:

• Fix for Union: now issubtype(Union[list, tuple], typing.Sequence) == True
• Fix None as an alias of type(None)
• Support TypeVar checking, while issubtype(TypeVar("T1"), TypeVar("T2")) == typing_utils.unknown
• Fix for Callable: Callable[[int], str] won't raise an exception anymore.