Mock user following PART 1

- Reached out my grubby hands into code that I wasn't supposed to touch
in app.js (minor changes, but let me know if it's bad, I don't know what
I'm doing I just did enough to make code run)
- Made usernamedb an associative database (I don't know what I'm doing
but once again, it makes code work)
- Added more fake data (trivial)
- Your home page now displays the latest twitt from users you're
following.

TODO:
- List twitts when you check profile pages of others
- Follow/unfollow others' profiles
- Show number of people following you.