Add pfp depending on the user colours to slack

[PPTide]

#154

Originally posted by @quackduck in #154 (comment)

[PPTide]

Maybe possible using this: https://api.slack.com/methods/chat.postMessage#authorship

[quackduck]

Unfortunately it looks like this requires an image URL too

[PPTide]

Could we use this website to create the images for us?

http://verumignis.com/

[quackduck]

I don't think we should depend on external services like that