fix crash on memoizing partial

[MichaelBlume]

functools.partial objects don't have module or name

this is arguably a problem with functools, but accomodate it anyway.

[MichaelBlume]

Anything I should be doing to help with this patch?

[tseaver]

Sorry for the delay. If you could address my line comments, along with the following two housekeeping bits, I would be glad to merge:

• Add a note describing the change to 'CHANGES.txt'.
• "Sign" the CONTRIBUTORS.txt by adding your name and the date at the bottom.

[tseaver]

Thanks!