Added equals implementations on model classes.

src/main/groovy/com/jdbernard/nlsongs/model/Performance.groovy

@@ -10,4 +10,22 @@ public class Performance implements Serializable {
     String drummer
     String guitarist
     String leader
+
+    @Override public boolean equals(Object thatObj) {
+        if (thatObj == null) return false
+        if (!(thatObj instanceof Performance)) return false
+
+        Performance that = (Performance) thatObj
+
+        return (this.serviceId == that.serviceId &&
+                this.songId == that.songId &&
+                this.pianist == that.pianist &&
+                this.organist == that.organist &&
+                this.bassist == that.bassist &&
+                this.drummer == that.drummer &&
+                this.guitarist == that.guitarist &&
+                this.leader == that.leader) }
+
+    @Override String toString() {
+        return "($serviceId, $songId): $leader - $pianist" }
 }