formatNumber to accept maximumFractionDigits=0

Logic error in the options processing that prevent
maximumFractionDigits=0 from being passed into internal methods
properly, resulting in maximumFractionDigits being set to default
value. Fixed the logic and added tests to ensure fraction truncation.

```Globalize.formatNumber(3.14159, {maximumFractionDigits: 0}) === "3"```
Same here.