fixed DateService to throw Exceptions instead of returning null

git-svn-id: http://jclouds.googlecode.com/svn/trunk@1868 3d8758e0-26b5-11de-8745-db77d3ebf521

core/src/main/java/org/jclouds/util/DateService.java

@@ -94,7 +94,7 @@ public class DateService {
          try {
             return new DateTime(rfc822SimpleDateFormat.parse(toParse));
          } catch (ParseException e) {
-            return null;
+            throw new RuntimeException(e);
          }
       }
    }
@@ -116,7 +116,7 @@ public class DateService {
          try {
             return new DateTime(iso8601SimpleDateFormat.parse(toParse));
          } catch (ParseException e) {
-            return null;
+            throw new RuntimeException(e);
          }
       }
    }