Fix up navigation when opening the app from widget

Fixes #94

app/src/main/AndroidManifest.xml

@@ -61,8 +61,7 @@
 
         <activity
             android:name=".ShowHabitActivity"
-            android:label="@string/title_activity_show_habit"
-            android:parentActivityName=".MainActivity">
+            android:label="@string/title_activity_show_habit">
             <meta-data
                 android:name="android.support.PARENT_ACTIVITY"
                 android:value="org.isoron.uhabits.MainActivity"/>
@@ -70,8 +69,7 @@
 
         <activity
             android:name=".SettingsActivity"
-            android:label="@string/settings"
-            android:parentActivityName=".MainActivity">
+            android:label="@string/settings">
             <meta-data
                 android:name="android.support.PARENT_ACTIVITY"
                 android:value="org.isoron.uhabits.MainActivity"/>
@@ -92,8 +90,10 @@
 
         <activity
             android:name=".AboutActivity"
-            android:label="@string/about"
-            android:parentActivityName=".MainActivity">
+            android:label="@string/about">
+            <meta-data
+                android:name="android.support.PARENT_ACTIVITY"
+                android:value=".MainActivity" />
         </activity>
 
         <receiver

app/src/main/java/org/isoron/uhabits/HabitBroadcastReceiver.java

@@ -33,6 +33,7 @@ import android.net.Uri;
 import android.os.Handler;
 import android.preference.PreferenceManager;
 import android.support.v4.app.NotificationCompat;
+import android.support.v4.app.TaskStackBuilder;
 import android.support.v4.content.LocalBroadcastManager;
 
 import org.isoron.uhabits.helpers.DateHelper;
@@ -244,7 +245,10 @@ public class HabitBroadcastReceiver extends BroadcastReceiver
     {
         Intent intent = new Intent(context, ShowHabitActivity.class);
         intent.setData(Uri.parse("content://org.isoron.uhabits/habit/" + habit.getId()));
-        return PendingIntent.getActivity(context, 0, intent, 0);
+
+        return TaskStackBuilder.create(context.getApplicationContext())
+                .addNextIntentWithParentStack(intent)
+                .getPendingIntent(0, PendingIntent.FLAG_UPDATE_CURRENT);
     }
 
     private boolean checkWeekday(Intent intent, Habit habit)