Color overflow button

Overflow button color is based of `options.topBar.rightButtonColor`, this might change in the future.

lib/android/app/src/main/java/com/reactnativenavigation/presentation/StackPresenter.java

         if (options.buttons.back.visible.isTrue() && !options.buttons.hasLeftButtons()) {
             topBar.setBackButton(createButtonController(options.buttons.back));
         }
+
+        topBar.setOverflowButtonColor(options.rightButtonColor.get(Color.BLACK));
     }
 
     private List<TitleBarButtonController> getOrCreateButtonControllers(@Nullable Map<String, TitleBarButtonController> currentButtons, @Nullable List<Button> buttons) {
         if (buttons.right != null) topBar.setRightButtons(rightButtonControllers);
         if (buttons.left != null) topBar.setLeftButtons(leftButtonControllers);
         if (buttons.back.hasValue()) topBar.setBackButton(createButtonController(buttons.back));
+
+        if (options.rightButtonColor.hasValue()) topBar.setOverflowButtonColor(options.rightButtonColor.get());
     }
 
     @Nullable

lib/android/app/src/main/java/com/reactnativenavigation/views/titlebar/TitleBar.java

 
 import android.annotation.SuppressLint;
 import android.content.Context;
+import android.graphics.PorterDuff;
+import android.graphics.PorterDuffColorFilter;
 import android.graphics.Typeface;
+import android.graphics.drawable.Drawable;
+import android.support.v7.widget.ActionMenuView;
 import android.support.v7.widget.Toolbar;
 import android.util.Log;
 import android.view.View;
         lp.height = pixelHeight;
         setLayoutParams(lp);
     }
+
+    public void setOverflowButtonColor(int color) {
+        ActionMenuView actionMenuView = ViewUtils.findChildByClass(this, ActionMenuView.class);
+        if (actionMenuView != null) {
+            Drawable overflowIcon = actionMenuView.getOverflowIcon();
+            if (overflowIcon != null) {
+                overflowIcon.setColorFilter(new PorterDuffColorFilter(color, PorterDuff.Mode.SRC_IN));
+            }
+        }
+    }
 }

lib/android/app/src/main/java/com/reactnativenavigation/views/topbar/TopBar.java

     public void setBorderColor(int color) {
         border.setBackgroundColor(color);
     }
+
+    public void setOverflowButtonColor(int color) {
+        titleBar.setOverflowButtonColor(color);
+    }
 }