Add showsCompass to MapView props

Summary: Was trying to remove the compass from the map and thought I would contribute to the project for everyone.
Closes https://github.com/facebook/react-native/pull/4225

Reviewed By: svcscm

Differential Revision: D2674060

Pulled By: nicklockwood

fb-gh-sync-id: 66f069dfc53fdeae8aaab76980146296cea1140f

Libraries/Components/MapView/MapView.js

@@ -87,6 +87,13 @@ var MapView = React.createClass({
      */
     showsPointsOfInterest: React.PropTypes.bool,
 
+    /**
+     * If `false` compass won't be displayed on the map.
+     * Default value is `true`.
+     * @platform ios
+     */
+    showsCompass: React.PropTypes.bool,
+
     /**
      * If `false` the user won't be able to pinch/zoom the map.
      * Default value is `true`.

React/Views/RCTMapManager.m

@@ -38,6 +38,7 @@ RCT_EXPORT_MODULE()
 
 RCT_EXPORT_VIEW_PROPERTY(showsUserLocation, BOOL)
 RCT_EXPORT_VIEW_PROPERTY(showsPointsOfInterest, BOOL)
+RCT_EXPORT_VIEW_PROPERTY(showsCompass, BOOL)
 RCT_EXPORT_VIEW_PROPERTY(zoomEnabled, BOOL)
 RCT_EXPORT_VIEW_PROPERTY(rotateEnabled, BOOL)
 RCT_EXPORT_VIEW_PROPERTY(pitchEnabled, BOOL)