fix: api cosmetic changes

Docs: Typo in Custom Annotations example

Android custom annotation bugfixes.

- Custom annotations would sometimes not get rendered on the screen.
  Haven't nailed down the exact problem, but it was some sort of
  interleaving of operations from adding children and computing custom
  marker views. Moving the marker view stuff to when the map finishes
  loading resolves this.
- The adapter for the react native marker views now handles the caching
  behaviour correctly and re-uses views when they are available.
- Make sure each layout actually gets the height and width of the react
  native views from the correct shadow nodes so that they don't all have
  the same measurements by accident.
- Update locations of annotations when they are changed.
- Split annotation views into a map. The manager is a singleton and all
  the existing map views go through it so the children need to be kep
  separately.
- Safeguard against relayout being called after onDrop(), resulting in a
  null pointer exception.

Merge branch 'feature/android-custom-annotations' of https://github.com/gillessed/react-native-mapbox-gl into gillessed-feature/android-custom-annotations

Upgrade android SDK to 4.2.2

Removed this pre-commit too hastily.

This gives feature parity to Custom Annotation Views
between iOS and Android.

- Add custom marker view and options for mapbox.
- Add an implementation for the Annotation class.
- Add a MarkerViewAdapater that transforms Annotations into views that
  get displayed on the map.
- Handle adding and removing of children.
- Update custom annotation docs.

ensure that MapboxAccountManager class is always created from the main thread; fixes crash from Android SDK 4.2.0-beta.4 and up (#517)

If script is being run from a path having spaces it will fail

to fix this crash: https://github.com/mapbox/mapbox-gl-native/issues/6838#issuecomment-269646230

I had a problem setting up RN mapboxgl to work on my system because of
this. I think a lot of macs are case insensitive, but not all.

RNPM is merged into React Native core - see [here](https://github.com/rnpm/rnpm/blob/master/README.md#dear-friends)

Adding onCloseAnnotation to iOS

* Add 5.1.0 changelog

* ‍♂️

Do not require access token for iOS

fix podspec

Fix typo in CocoaPods instructions

PropTypes.object() is not a function. Use shape() instead.

`PropTypes.object` is not a function — use `.shape` instead. Should remove the following error message from the console:

```
<Warning>: Warning: You are manually calling a React.PropTypes validation function for the `undefined` prop on `<<anonymous>>`. This is deprecated and will not work in the next major version. You may be seeing this warning due to a third-party PropTypes library. See https://fb.me/react-warning-dont-call-proptypes for details.
```

"wether" > "whether" typo in docs