Fixed doctests around 'assigned'

[benoitbryon]

This pull-requests is based on https://github.com/zeekay/decorum/pull/15. In https://github.com/zeekay/decorum/pull/15, "build fails if doctests fail", but doctests actually fail. Here, I added a fix for the doctests, but I'm not sure about the implementation. So you may accept one pull-request but not the other...

Here, I did a change in the behaviour of the assigned feature. Check changes in README:

• default value for assigned is now functools.WRAPPER_ASSIGNMENTS, see https://docs.python.org/2.7/library/functools.html#functools.update_wrapper. It adds __module__ to the default value. I think it is good to be consistent with Python's standard library. That said, I can restore the former default if you like, and create a new pull-request/discussion for this change. Just tell me ;)
• is assigned is None, then __name__ and __doc__ of the decorated object are the ones of the decorator class, i.e. identity and Noop decorator: does nothing! instead of None and None. I think it is more consistent... That said, again, I can restore the former behaviour, and perhaps ask for this change in a new pull-request/discussion. Just tell me ;)

What's important here is that doctests are fixed!

[benoitbryon]

Hum, I think I will restore the former behaviour and focus on fixing the doctests here... So the behaviour changes are not part of this deal...

[benoitbryon]

Ahaha, functools.WRAPPER_ASSIGNMENTS is not the same in Python2 and Python3... Let's restore ('__name__', '__doc__') and try functools later, in another PR.

[benoitbryon]

Done, doctests pass, with minimal changes of behaviour.

I had to change the README, because print(my_function.__name__) actually outputs None when the name is None.

[benoitbryon]

https://travis-ci.org/zeekay/decorum/jobs/73708648#L165-L171 Looks like it would also fix #8.

[zeekay]

Cool!