Overriding units

[ticky]

I'd like to know how you might suggest implementing Numeral in an application which needs to display both bits and bytes, as well as requiring decimal and binary prefixed versions for each.

I'm happy to work towards a pull request with such functionality, but given the way the API is put together at present, I can't see any clean way to specify multiple behaviours, or even just parameters.

[adamwdraper]

Done!