fix license to conform to BSD standard

[replygirl]

hello!

looks like your license uses the boilerplate for 4-clause (a.k.a. original), but you've removed the advertising clause so the content is in line with 3-clause

to have an unambiguously valid license, you'll need to either add back the advertising clause to conform to 4-clause, or switch our the copy to conform to 3-clause

if neither change is made and a django-money user ends up in litigation regarding ownership or copyright, it's possible the user won't be able to claim full rights to their own code