Go S3 Uploader
- implement optimizations as per https://aws.amazon.com/articles/1904/ , the "Optimizing Network Performance" section in particular;
- implement (optional) MD5 verification (see Content-MD5 at http://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectPUT.html);
- implement multipart uploads + non "slurp mode" file read (+ make the limit where multipart kicks in configurable);
- implement deletion of remote files missing on local;
- (maybe) implement config file (from curr dir/home);


