Make Resource comparable.

src/main/java/com/threerings/getdown/data/Resource.java

@@ -25,7 +25,7 @@ import static com.threerings.getdown.Log.log;
 /**
  * Models a single file resource used by an {@link Application}.
  */
-public class Resource
+public class Resource implements Comparable<Resource>
 {
     /**
      * Computes the MD5 hash of the supplied file.
@@ -292,6 +292,10 @@ public class Resource
         }
     }
 
+    @Override public int compareTo (Resource other) {
+        return _path.compareTo(other._path);
+    }
+
     @Override public boolean equals (Object other)
     {
         if (other instanceof Resource) {