python2: is_confusable cannot handle unicode preferred_aliases

[muusik]

(Thanks for creating such a useful tool that confusable_homoglyphs is)
Since the return type of categories.alias() is unicode when running in Python 2, it would make sense that preferred_alias argument of confusables.is_confusable() would accept a list of same, but it requires list of strings instead, otherwise giving a TypeError. An example follows:

>>> from confusable_homoglyphs import confusables
>>> confusables.is_confusable('', preferred_aliases=[u'LATIN'])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/confusable_homoglyphs/confusables.py", line 92, in is_confusable
    preferred_aliases = list(map(str.upper, preferred_aliases))
TypeError: descriptor 'upper' requires a 'str' object but received a 'unicode'

[vhf]

Nice, thanks for the issue and the fix!

I'm glad this lib is useful to you. Care to share what your use case for it?

[muusik]

Sure, our use case is closing a potential loophole in a plagiarism detection system. Thanks for pushing the update in such timely fashion.