Fix a big bunch of lint warning

app/src/main/java/com/cappielloantonio/play/broadcast/receiver/ConnectivityStatusBroadcastReceiver.java

@@ -9,7 +9,7 @@ import android.view.View;
 import com.cappielloantonio.play.ui.activity.MainActivity;
 
 public class ConnectivityStatusBroadcastReceiver extends BroadcastReceiver {
-    private MainActivity activity;
+    private final MainActivity activity;
 
     public ConnectivityStatusBroadcastReceiver(MainActivity activity) {
         this.activity = activity;

app/src/main/java/com/cappielloantonio/play/broadcast/receiver/MediaButtonIntentReceiver.java

@@ -47,7 +47,7 @@ public class MediaButtonIntentReceiver extends BroadcastReceiver {
     private static long mLastClickTime = 0;
 
     @SuppressLint("HandlerLeak")
-    private static Handler mHandler = new Handler() {
+    private static final Handler mHandler = new Handler() {
 
         @Override
         public void handleMessage(final Message msg) {