update and tweak tqdm progressbar

[casperdcl]

This is a follow-on from #242.

• update to latest version of tqdm>=4.14
  • use unit_divisor=1024 instead of 1000
• use 'B' as units instead of 'bytes'
• leave progressbar upon completion (to match old behaviour when clint was used, and to look pretty and provide permanent info)

external:

• ensure users can download tqdm>=4.14 via:
  • pypi
  • conda

thanks for using tqdm!

[codecov-io]

Codecov Report

Merging #256 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master     #256   +/-   ##
=======================================
  Coverage   67.01%   67.01%           
=======================================
  Files          12       12           
  Lines         573      573           
  Branches       91       91           
=======================================
  Hits          384      384           
  Misses        162      162           
  Partials       27       27

Impacted Files	Coverage Δ
twine/repository.py	59.8% <0%> (ø)	⬆️

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[casperdcl]

looks good to merge

[sigmavirus24]

Thanks @casperdcl!