Style tabs, add missing drawables

OpenKeychain/src/main/res/layout/help_activity.xml

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     android:layout_width="match_parent"
     android:layout_height="match_parent">
 
@@ -9,15 +10,17 @@
 
     <LinearLayout
         android:layout_below="@id/toolbar"
-
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:orientation="vertical">
 
-        <org.sufficientlysecure.keychain.ui.widget.SlidingTabLayout
+        <com.astuetz.PagerSlidingTabStrip
             android:id="@+id/sliding_tab_layout"
             android:layout_width="match_parent"
-            android:layout_height="wrap_content" />
+            android:layout_height="?attr/actionBarSize"
+            android:background="?attr/colorPrimary"
+            android:textColor="#FFFFFF"
+            app:pstsIndicatorColor="#FFFFFF" />
 
         <android.support.v4.view.ViewPager
             android:id="@+id/pager"