Example now preserves collection order (closes #38)

accumulate/example.java

 import java.util.ArrayList;
-import java.util.Collection;
 import java.util.List;
 import java.util.function.Function;
 
 public class Accumulate {
 
-	public static <T> Collection<T> accumulate(Collection<T> collection, Function<T, T> function) {
+	public static <T> List<T> accumulate(List<T> collection, Function<T, T> function) {
 		List<T> newCollection = new ArrayList<>();
 
 		for (T item : collection) {