Changes runtime to SAX exception in TrenesContentHandler

The SAXException is more adequate than the RuntimeException.

src/main/java/es/uvigo/esei/dai/xml/tests/TrenesContentHandler.java

@@ -39,7 +39,7 @@ public class TrenesContentHandler extends DefaultHandler {
       try {
         this.lastDate = Tren.DATE_FORMAT.parse(textContent);
       } catch (final ParseException pe) {
-        throw new RuntimeException("Invalid date: " + textContent, pe);
+        throw new SAXException("Invalid date: " + textContent, pe);
       }
     }
   }