Change the repliesTo for post from list -> set.

This removes the bug when a post seems to have more replies than it
should due to people quoting the post number more than once in their
post.
This also fixes the bug where the post1 that quotes post2 multiple
times, post1 shows up in the list of replies for post2 multiple times.

Clover/app/src/main/java/org/floens/chan/core/model/Post.java

@@ -29,6 +29,8 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.Random;
+import java.util.Set;
+import java.util.TreeSet;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 /**
@@ -104,9 +106,9 @@ public class Post {
 
 
     /**
-     * This post replies to the these ids. Is an unmodifiable list after finish().
+     * This post replies to the these ids. Is an unmodifiable set after finish().
      */
-    public List<Integer> repliesTo = new ArrayList<>();
+    public Set<Integer> repliesTo = new TreeSet<>();
 
     public final ArrayList<PostLinkable> linkables = new ArrayList<>();
 
@@ -182,7 +184,7 @@ public class Post {
 
         ChanParser.getInstance().parse(this);
 
-        repliesTo = Collections.unmodifiableList(repliesTo);
+        repliesTo = Collections.unmodifiableSet(repliesTo);
 
         return true;
     }