Util.operators: allow variadic methods to work with arrays

Variadic util operators, such as _.add(), can now work with argument arrays.

e.g. `_.add([1,2,3]) === 6`
Avoid arguments[0] here there and everywhere
On Oct 20, 2014 1:43 PM, "jacobpurcell" <notifications@github.com> wrote:

> In underscore.util.operators.js:
>
> > @@ -16,7 +16,8 @@
> >    // Turn a binary math operator into a variadic operator
> >    function variadicMath(operator) {
> >      return function() {
>
> Why?
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/documentcloud/underscore-contrib/pull/180/files#r19100441>
> .
>