On startup, the code now initializes MEDIA with suitable media files
found in the `media` directory that satisfy Twitter's media file
requirements. The `filetype` Python module has been added as a
dependency to ensure that files in `media` are what they claim to be.
In the bot class I added a new _parse_mention method, broke up the
pasta chain builder method, and added a new recursive _tweet_media
method. The _parse_mention method had to have some `stupid_emoji`
hackery thanks to the way the 🖼 emoji gets encoded in some tweets.
A new fetch-media script has been added along with a new util function
See media/README.md for more information on how to use the newly-added