Set pair class to implement serializable (#128)

Author: Shelnutt2

src/main/java/io/tiledb/java/api/Pair.java

@@ -24,7 +24,7 @@
 
 package io.tiledb.java.api;
 
-public class Pair<F, S> {
+public class Pair<F, S> implements java.io.Serializable {
   private F first;
   private S second;