Update jquery.fileupload-validate.js

This helps validation work more accurate. I don't know why but data.files[data.index].size is always greater then data.originalFiles[data.index].size so the validation get incorrect. I set the maxFilesize = 5MB and try to upload a 4.5MB file but it didn't work. Then I finally figured it out: the retrieved file size become 7MB !
Thanks for making such awesome plugin.