Issue title: File size calculation
 Issue body: It seems file size is not calculated correctly. I tried one 1MB file (1024x1024 Bytes). And it reports the file as 1.05 MB

 Comments: 
 Comment 0: The plugin itself does not do any file size calculations.

However, the [demo ](http://aquantum-demo.appspot.com/file-upload) does some calculations based on these two simple functions:

```
var roundDecimal = function (num, dec) {
        return Math.round(num * Math.pow(10, dec)) / Math.pow(10, dec);
    },
    formatFileSize = function (bytes) {
        if (isNaN(bytes) || bytes === null) {
            return '';
        }
        if (bytes >= 1000000000) {
            return roundDecimal(bytes / 1000000000, 2) + ' GB';
        }
        if (bytes >= 1000000) {
            return roundDecimal(bytes / 1000000, 2) + ' MB';
        }
        return roundDecimal(bytes / 1000, 2) + ' KB';
    };
```

The calculations are according to the [International Systems of Units](http://physics.nist.gov/cuu/Units/binary.html), whereas one megabyte (1 MB) = 1000000 Bytes.
Please refer to Wikipedia on the controversy between MB, MiB, 1000 and 1024 for unit measurement for [Megabyte](http://en.wikipedia.org/wiki/Megabyte), [Kilobyte](http://en.wikipedia.org/wiki/Kilobyte), etc.

 Comment 1: cool, thanks for the info.

{'source': 'GithubIssues', 'repo_name_with_owner': 'blueimp/jQuery-File-Upload', 'issue_id': 568765, 'repo_stars': 31053.0}