function interpolation(name, method) {
	if (name && method) {
		interpolation[name] = method;
	} else if (name && interpolation[name] instanceof Function) {
		Sink.interpolate = interpolation[name];
	}
	return interpolation[name];
}
If method is supplied, adds a new interpolation method to Sink.interpolation, otherwise sets the default interpolation method (Sink.interpolate) to the specified property of Sink.interpolate.

@arg {String} name The name of the interpolation method to get / set.
@arg {Function} !method The interpolation method.