Implement md5c function, slower than Golang's implementation

keeping it in repo to make further improvements and also rename

        minio-hash ---> crypto

pkgs/crypto/md5/md5.go

@@ -8,10 +8,15 @@ import (
 func Sum(reader io.Reader) ([]byte, error) {
 	hash := md5.New()
 	var err error
+	var length int
 	for err == nil {
-		length := 0
 		byteBuffer := make([]byte, 1024*1024)
 		length, err = reader.Read(byteBuffer)
+		// While hash.Write() wouldn't mind a Nil byteBuffer
+		// It is necessary for us to verify this and break
+		if length == 0 {
+			break
+		}
 		byteBuffer = byteBuffer[0:length]
 		hash.Write(byteBuffer)
 	}