perf(isArray): use native Array.isArray

Request Type: perf

How to reproduce: 

Component(s): misc core

Impact: small

Complexity: small

This issue is related to: 

**Detailed Description:**



**Other Comments:**

see benchmark: http://jsperf.com/isarray-performance
also, I don't think we need to worry about it living in the Array prototype, or the Array static --- it should work either way.

Just `if (!isFunction(Array.isArray)) {` should be fine