VVM should not use tqdm unless tqdm is installed

[sabotagebeats]

vvm/vvm/install.py

Lines 24 to 27 in 1c562ed

	try:
	from tqdm import tqdm
	except ImportError:
	tqdm = None

[iamdefinitelyahuman]

tqdm is only required if vvm.install_vyper is called with the show_progress kwarg set to True. The docstring for this method states that when using show_progress you must have installed tqdm. In my mind this isn't an issue, as you can mitigate it by not requesting a progress bar or including tqdm as an upstream dependency.

[fubuloubu]

Makes sense!