DX-2226 Updated XML Declaration

Author: ckoegel

src/main/java/com/bandwidth/voice/bxml/verbs/Response.java

@@ -121,6 +121,7 @@ private Marshaller getMarshaller() {
             }
             Marshaller marshaller = jaxbContext.createMarshaller();
             // omits <?xml version="1.0" encoding="UTF-8"?>
+            marshaller.setProperty("com.sun.xml.bind.xmlHeaders", "<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
             marshaller.setProperty(Marshaller.JAXB_FRAGMENT, true);
 
             return marshaller;