Pre-lollipop compatible issue fixed

Author: jemshit

material_preferences_library/src/main/res/drawable-v21/mpl__custom_ripple_effect_background.xml

@@ -0,0 +1,10 @@
+<ripple
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:color="#a5a5a5">
+    <item>
+        <shape
+            android:shape="rectangle">
+            <solid android:color="@android:color/transparent" />
+        </shape>
+    </item>
+</ripple>

material_preferences_library/src/main/res/drawable/mpl__custom_ripple_effect_background.xml

@@ -1,12 +1,21 @@
-<ripple
-    xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:tools="http://schemas.android.com/tools"
-    android:color="#a5a5a5"
-    tools:targetApi="lollipop">
+<selector
+    xmlns:android="http://schemas.android.com/apk/res/android">
     <item>
         <shape
             android:shape="rectangle">
             <solid android:color="@android:color/transparent" />
         </shape>
     </item>
-</ripple>
+    <item android:state_pressed="true">
+        <shape
+            android:shape="rectangle">
+            <solid android:color="@android:color/transparent" />
+        </shape>
+    </item>
+    <item android:state_focused="true">
+        <shape
+            android:shape="rectangle">
+            <solid android:color="@android:color/transparent" />
+        </shape>
+    </item>
+</selector>