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"```

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Review:

- [x] Implementation;
- [x] [jQuery coding style](http://contribute.jquery.org/style-guide/js);
- [x] Unit and functional tests;
- [x] Documentation;