move integration test to appropriate folder

Author: anastasiia-kryshtop

src/test/java/com/exacttarget/fuelsdk/ETDataExtensionAdditionalTest.java renamed to src/integration-test/java/com/exacttarget/fuelsdk/ETDataExtensionIntegrationTest.java

@@ -14,7 +14,7 @@
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assume.assumeNotNull;
 
-public class ETDataExtensionAdditionalTest {
+public class ETDataExtensionIntegrationTest {
 
     private ETClient client;