Add PGP support

[hyp3ri0n-ng]

I'd like to add additional protection via PGP. The user reqs are this: a user can insert their private PGP key to decrypt others' messages. A user should be able to also insert other chatters' public PGP keys so they can encrypt messages. It'd be cool if this was seamless in the sense that the user doesn't need to do anything additional to decrypt messages from various users. Not sure on the best way to do this :-), but it should be client-side, likely in JS, and hopefully easy to follow for code reviews (a goal of this project is to make reviewing the code easy - a problem I find in a lot of open source software).