Better config check.
Better config check.

Or it will bomb for:

```js
> easydate('d-M-Y @ h:m', '2015-11-03T16:06:00.000Z')
TypeError: Cannot use 'in' operator to search for 'setDate' in 2015-11-03T16:06:00.000Z
```
roryrjb/easydate