Please provide real distfiles for the releases #131

Hi,

In order to be able to cleanly package libgit2 for freebsd we need to get some "true distfiles".

github guys also think that the tags aren't clean distfiles:
http://support.github.com/discussions/repos/4017-tags-and-distfile-generation-issues

The main problem for us is the http redirection. With true distfiles we can access a directly link with no redirection: cloud.github.com with tags we can't plus the checksum changes each time the tarball associated to the tag is regenerated by github.

Thanks,
Bapt