rewrite download_community.sh

[llimllib]

This PR is a rewrite of download_commity.sh. Its primary focus is readability and compatibility with older bash versions. (see https://github.com/juncongmoo/pyllama/issues/47#issuecomment-1499265114 for why it doesn't work with bash 3, which (unfortunately) is mac's default bash version).

• remove use of associative arrays for compatibility with bash 3
• move repetitive tasks into functions and add comments
• use a simpler method to join URL paths
• add usage information, as well as the -h and -v arguments for "help" and "verbose respectively
• use color to better show the user what the script is up to
• check for wget and give the user an error if they don't have wget installed

I tested it by doing /bin/bash download_community.sh 7B,13B /tmp/llama-models on an m1 mac, which runs the script with bash 3.2.57.

Shellcheck reports no warnings:

$ shellcheck download_community.sh

on the version of the script in main, it shows many warnings.

[mldevorg]

This branch has conflicts that must be resolved.... Can you please resolve the conflicts? @llimllib Thank you.

[llimllib]

👍 fixed

[blah-mad]

please merge, it's 4 am here and i have been looking at this PR dead straight for the last 20 mins.

P.s. tons of thank you and a happy easter! ⭐ 🥚