Warning when using google.maps.MVCArray in Polyline path

The MVCArray **totally** works when it renders, but it just pops up an annoying warning to the console. And more importantly, it lets me add LatLngs to the MVCArray async'ly.

```
Warning: Invalid prop `path` of type `object` supplied to `Polyline`, expected `array`. Check the render method of `ReactFrag`.
```

This is an issue of the frag being too tight in PropTypes?
