Update readme to mention tqdm

Author: asivery

README.md

@@ -178,6 +178,7 @@ One thing you need to pay attention to here is, that the unmount command continu
 The [`ltfs_ordered_copy`](https://github.com/LinearTapeFileSystem/ltfs/wiki/ltfs_ordered_copy) is a program to copy files from source to destination with LTFS  order  optimization.
 
 It is written in python and it can work with both python2 and python3 (Python 2.7 or later is strongly recommended). You need to install the `pyxattr` module for both python2 and python3.
+For nicer-looking progress bars while copying, it is also recommended you install `tqdm`.
 
 # Building the LTFS from this GitHub project