* fix tqdm unit_scale and support hours in time
previously it only supports MM:SS.
more chars to unitscales, strip trailing "." and " " in formatting, and more tests
* simpler
per doc `https://tqdm.github.io/docs/tqdm/`, user does not need to put `: ` in desc, and `: ` is automatically removed after desc if the latter is empty.
updated test cases and added a test for set_description
