Update AirMapMarker to use loadImageWithURLRequest (#389)
Update AirMapMarker to use loadImageWithURLRequest (#389)

[`loadImageWithTag`](https://github.com/facebook/react-native/blob/ba4c34c0db004cda9fb561b3bdf5224d518ab32d/Libraries/Image/RCTImageLoader.m#L755) is deprecated and shows warnings on RN 0.29.

### Test Plan

On iOS, render a map with a marker that has image prop set. See marker is rendered correctly and no deprecation warnings.

```
<MapView ...>
  <MapView.Marker ... image={require('./pin.png')} />
</MapView>
```
lelandrichardson/react-native-maps,pjamrozowicz/react-native-maps,pjamrozowicz/react-native-maps,parkling/react-native-maps,amitv87/react-native-maps,hlz2103/SwipeMe,lelandrichardson/react-native-maps,jrichardlai/react-native-maps,hlz2103/SwipeMe,zigbang/react-native-maps,pjamrozowicz/react-native-maps,amitv87/react-native-maps,azt3k/react-native-maps,carleryd/react-native-maps,palexs/react-native-maps,ali-alamine/react-native-maps,mvakulich/react-native-maps,hzdg/react-native-maps,jiaminglu/react-native-maps,zigbang/react-native-maps,palexs/react-native-maps,hzdg/react-native-maps,j0ergo/react-native-maps,j0ergo/react-native-maps,amitv87/react-native-maps,Nabobil/react-native-maps,jiaminglu/react-native-maps,tt-sport-mobile/react-native-maps,tt-sport-mobile/react-native-maps,wannyk/react-native-maps,ksincennes/react-native-maps,hlz2103/SwipeMe,Nabobil/react-native-maps,athaeryn/react-native-maps,adamivancza/react-native-maps,mvakulich/react-native-maps,phantomlds/react-native-maps,ksincennes/react-native-maps,jrichardlai/react-native-maps,hzdg/react-native-maps,wannyk/react-native-maps,ksincennes/react-native-maps,jrichardlai/react-native-maps,palexs/react-native-maps,Nabobil/react-native-maps,azt3k/react-native-maps,wannyk/react-native-maps,parkling/react-native-maps,parkling/react-native-maps,azt3k/react-native-maps,phantomlds/react-native-maps,adamivancza/react-native-maps,athaeryn/react-native-maps,lelandrichardson/react-native-maps,carleryd/react-native-maps,jiaminglu/react-native-maps,mvakulich/react-native-maps,tt-sport-mobile/react-native-maps,zigbang/react-native-maps,carleryd/react-native-maps,ali-alamine/react-native-maps,adamivancza/react-native-maps,j0ergo/react-native-maps,wannyk/react-native-maps,athaeryn/react-native-maps,ali-alamine/react-native-maps,phantomlds/react-native-maps