enqueue and dequeue implemented

StackTest.ctxt

@@ -0,0 +1,11 @@
+#BlueJ class context
+comment0.target=StackTest
+comment1.params=
+comment1.target=void\ testePush()
+comment2.params=
+comment2.target=void\ testePop()
+comment3.params=
+comment3.target=void\ testeTop()
+comment4.params=
+comment4.target=void\ testeIsEmpty()
+numComments=5