Expose pitchEnabled property (#407)

* Expose the 'pitchEnabled' property, so developer can turn off 'two-fingers to tile map' feature. iOS-only so far.

* Add `pitchEnabled` property to Android implementation

* add `pitchEnabled` to docs

android/src/main/java/com/mapbox/reactnativemapboxgl/ReactNativeMapboxGLManager.java

@@ -131,6 +131,11 @@ public class ReactNativeMapboxGLManager extends SimpleViewManager<ReactNativeMap
         view.setZoomEnabled(value);
     }
 
+    @ReactProp(name = "pitchEnabled")
+    public void setPitchEnabled(ReactNativeMapboxGLView view, boolean value) {
+        view.setPitchEnabled(value);
+    }
+
     @ReactProp(name = "showsUserLocation")
     public void setShowsUserLocation(ReactNativeMapboxGLView view, boolean value) {
         view.setShowsUserLocation(value);

android/src/main/java/com/mapbox/reactnativemapboxgl/ReactNativeMapboxGLView.java

@@ -56,6 +56,7 @@ public class ReactNativeMapboxGLView extends RelativeLayout implements
     private boolean _trackingModeUpdateScheduled = false;
     private boolean _showsUserLocation;
     private boolean _zoomEnabled = true;
+    private boolean _pitchEnabled = true;
     private boolean _scrollEnabled = true;
     private boolean _rotateEnabled = true;
     private boolean _enableOnRegionWillChange = false;
@@ -148,6 +149,7 @@ public class ReactNativeMapboxGLView extends RelativeLayout implements
         uiSettings.setZoomGesturesEnabled(_zoomEnabled);
         uiSettings.setScrollGesturesEnabled(_scrollEnabled);
         uiSettings.setRotateGesturesEnabled(_rotateEnabled);
+        uiSettings.setTiltGesturesEnabled(_pitchEnabled);
 
         // If these settings changed between setupMapView() and onMapReady(), coerce them to their right values
         // This doesn't happen in the current implementation of MapView, but let's be future proof
@@ -252,6 +254,14 @@ public class ReactNativeMapboxGLView extends RelativeLayout implements
         }
     }
 
+    public void setPitchEnabled(boolean value) {
+        if (_pitchEnabled == value) { return; }
+        _pitchEnabled = value;
+        if (_map != null) {
+            _map.getUiSettings().setTiltGesturesEnabled(value);
+        }
+    }
+
     public void setStyleURL(String styleURL) {
         if (styleURL.equals(_mapOptions.getStyle())) { return; }
         _mapOptions.styleUrl(styleURL);