Added proper .equals and hashCode methods for Keyframes

src/main/java/eu/crushedpixel/replaymod/holders/Keyframe.java

@@ -11,4 +11,17 @@ public class Keyframe {
     public int getRealTimestamp() {
         return realTimestamp;
     }
+
+    @Override
+    public boolean equals(Object o2) {
+        if(o2 == null) return false;
+        if(!(o2 instanceof Keyframe)) return false;
+        Keyframe kf = (Keyframe)o2;
+        return hashCode() == kf.hashCode();
+    }
+
+    @Override
+    public int hashCode() {
+        return realTimestamp;
+    }
 }