Weird bug seems to be gone.

- My guess is it was caused by Wordfall's occupying the same column and overlapping each other. The previous commit's attempt at preventing this was not working correctly, but now is and the bug is gone. Yay!
Wordfalls now have text and some cool CSS.

- New code to add text to a column on construction of a Wordfall. A side effect of this is that if a Wordfall is created in an already occupied column (and is not overlapping; that's been fixed), the whole column's text will change, which was not an intended effect, but isn't too noticeable and actually looks kind of cool if you do notice it. So I intend to keep this feature.
- Refactored some code into helper functions, specifically code that was formerly in run() that involved generating random stuff.
- The grid effect seems kind of fucked up with the text and the screen doesn't fill entirely so that will be the next thing to work on along with possibly creating Wordfall's that advance at different speeds.