Set Locale to US

Currently when floats are rendered in my computer, they use `2,000`. Although this is the way the arena is currently doing it, it has been called a bug : http://apps.topcoder.com/forums/module=Message&messageID=1824120 

Since the rest of the problem statement uses US formatting, it is best for the time limit to use it too. 

For code we'll need a formatter / locale that is ensured to give code-friendly numbers. Locale.US might work, I think.