Using `Object.prototype.toString.call()` to check array type

Using `Object.prototype.toString.call()` to check array type instead of `toString.call()`. The latter, taken from lodash, doesn't work in IE! The former is taken from the recommended polyfill on [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/isArray).

Sorry about that Romu, I imagine the MDN polyfill will have better support.