Fix: Fifth option should be optional (#129)

Author: stipsan

src/index.js

@@ -1,6 +1,6 @@
 import animate from 'amator'
 
-export default function (elem, centerIfNeeded, options, finalElement, config) {
+export default function (elem, centerIfNeeded, options, finalElement, config = {}) {
 
   if (!elem) throw new Error('Element is required in scrollIntoViewIfNeeded')
 
@@ -80,4 +80,4 @@ export default function (elem, centerIfNeeded, options, finalElement, config) {
                             clientTop - parent.scrollTop);
       elem = parent;
   }
-}
+}