Python3, dependency updates, encryption changes

[Kenneth-W-Chen]

A lot's changed with Python and the various packages used by this program since it was last updated. A summary of what I changed:

• Change file encryption to AES-GCM
• !!!Key generation is done with argon2id!!!
  • These 2 changes should hopefully fix crypto issues mentioned in Multiple cryptography issues #10
• Fixed most/all praw functions/properties to the most current ones as of this PR
• Program now sleeps every 10-21 comments. This is because Reddit will likely auto-ban you if you try and send hundreds of comments at a time (or so my friend says)
  • I got by fine sending files around 3kb-100kb, which is about 3-10 comments. Maybe this limit needs to be lower?
• Adjustedcode to fit changes from Python2 to Python3 (print, bytes being a separate type from string, etc.)
• Removal of the username/password/subreddit fields from the window. These now go in praw.ini or redditglobals.py.
• A bit of code reformatting (some PEP conventions and variable renaming)
• Code is executed in a separate file from RedditStorage.py. Mainly did that because to make it easier to see how the script is started.
• Added some example files
• Changed requirements listed in the README (Most importantly, changed pycrypto to pycryptodome)
• Added more info to the README and fixed markdown issues

[Kenneth-W-Chen]

I'll be adding more comments/documentation over the next few weeks (unless PR gets approved)

[Kenneth-W-Chen]

I want to say a1b22ea will make it slightly faster because we don't have to load the entire file into memory and then encrypt it, with both the ciphertext and plaintext stored at once

[Kenneth-W-Chen]

I'm guessing that rossem isn't maintaining this repo anymore since there's been an open PR since 2018. I will not be pushing to this PR/branch any further. I'll be pushing to my fork for now here