dirty-equals causes a infinite-loop if it is used with functools.singledispatch

[15r10nk]

The following code causes a infinite-loop inside functools.singledispatch

from dirty_equals import IsStr

from functools import singledispatch


@singledispatch
def dispatch(a):
    print("generic", a)


s = IsStr()
dispatch(s)

It looks like this is caused by the fact that IsStr == IsStr is False.

I already created a pull-request, please let me know if this can be fixed this way.