Expected behavior: set_description() takes effect immediately when called

Actual behavior: set_description() takes effect only when .update() is called.

Steps to reproduce

import time

with tqdm(total=10, miniters=1, mininterval=0) as progress:
    for i in range(10):
        progress.set_description("step " + str(i + 1))
        time.sleep(0.5)
        progress.update()

Python version 3.5.2, TQDM version 4.10.0-10bd71