Allow setting of fileupload options through s3uploader

This is a fairly simple change to address #125. I created a new settings option called fileupload_options which defaults to null. By passing any valid option from https://github.com/blueimp/jQuery-File-Upload/wiki/Options you can set the option directly in the fileupload plugin.

I simply moved all of the fileupload function overrides to an api object and them extended them with the new settings option. I intentionally made it so that someone could override even the s3uploader default API in case they wanted to extend it.

Let me know if you have any questions.