remove 5MB minimum Javascript check.  <5MB allowed by AWS

I tested this with files < 5MB in size and they are uploaded successfully to AWS.   I think this must have been an older restriction.   AWS states in [quick facts](http://docs.aws.amazon.com/AmazonS3/latest/dev/qfacts.html) the last part of a multipart upload can be < 5 MB, and perhaps if there is only a single part, it treats it similarly.