[CHORE] Currency: JavaScript has Math.exp for e^x, so we should use it.
[CHORE] Currency: JavaScript has Math.exp for e^x, so we should use it.

ripple/ripple-lib,wilsonianb/ripple-lib,ripple/ripple-lib,ripple/ripple-lib,darkdarkdragon/ripple-lib,wilsonianb/ripple-lib,wilsonianb/ripple-lib,ripple/ripple-lib,darkdarkdragon/ripple-lib,darkdarkdragon/ripple-lib