Support maxFileSize, maxFiles, and maxUploadSize about resumable.js

[garjitech]

I was also considering adding an option which would allow the user to specify an external validation function (e.g. for possible server side validation).

Your thoughts?

[steffentchr]

My quick thoughts on maxFiles are on #17 and #25 -- and #25 was just merged in.

I think maxFiles can be handled as a special case, because we might want to clear the multiple option in the file input when the value is set to 1. For any other kind of validation/verification (whether total upload sizes, file type, names, or even reading of the files) I like your idea of having a callback. I would implement it by sending an array of file objects to the function -- which in turn would manipulate that data and return an array of the files to be included in the request. So basically and filter.

Would that work for your case?