Feature: Stock Ticker

[davepl]

We need a stock ticker effect. It should use an API that is free and for which the user can sign up for their own key, so that everyone is not using the same API key, unless it's unlimited (even bettter!).

Ticker should cycle through the specified stocks at some interval. It would be nice if it showed current and change, used color to indicate up vs down, and so on. Look at other stock tickers to see what functionality is included (but don't overtly copy anyone's design!).