Use BigDecimal instead of Float

Float is not suitable for money calculations since it gets rounding errors by design. It's not best practise to use them when money is involved.

The wiki docs should also be updated to use BigDecimal in examples. Possibly the lib should raise if given floats as input.

I suspect you've been bitten by this already as I found a test dealing with `130.45 * 3 => 391.34999999999997`.