Set CurrencyPrecision default value to 0

[take]

since 0 for int means empty,

&generator.Options{CurrencyPrecision: 0}

doesn't work unless we set the default value to 0

[angelodlfrtr]

Hi @take,

Thank you very much for your PR.

I think precision of 2 is a good default. One solution here should be to use pointers in Options fields so 0 would not be considered as a null value by the default library.

However it will break the current api so it will be part of a new major release.