Support format currency

Support format currency, extending `formatNumber` to able to format currency. Currencies are also numbers, they're a part of Number module.

#### TODO
- [ ] Implementation
- [ ] Unit and Functional tests
- [ ] Docs;

#### API Examples

     Globalize.formatNumber( 123.45, { currency: "EUR" } );
     Globalize.formatNumber( 53.07, { currency: "USD" } );

Adds currency as option

#### CLDR
- [Number Patterns](http://cldr.unicode.org/translation/number-patterns) 
- [Currency Symbols & Names](http://cldr.unicode.org/translation/currency-names)


Reference: https://github.com/jquery/globalize/issues/238