adding download & unzipping progress bar & download as stream

[luhangsnn]

(#34)
added downloading and unzipping progress bar to the download method that displays the file size, chunk size, and estimated finishing time.

minor issue for unzipping: when running on jupyter notebook, the output will first print a separate progress bar that will end at ~1% and then the proper progress bar for unzipping. This issue does not happen when testing in powershell terminal - have not found a solution to this jupyter-specific issue yet

I believe it also splits the download into chunks - 1024 bytes at a time (download as stream?) so that we don't need to hold the whole dataset in memory when downloading.
with requests.get(url, stream=True) as r
then
for chunk in r.iter_content(chunk_size=1024):

[nalmadi]

Thank you! You made a 2nd pull-request so I am closing this one.