Appending a date to the output file is now working.

This commit should resolve issue #1. Appending a date to the output file
is now a selectable option in the app configuration.

MergePDFs.cs

@@ -77,6 +77,12 @@
             }
             return pdfFiles;
         }
+
+        public static string GetDate()
+        {
+            DateTime date = DateTime.Now;
+            return date.ToString("yyyy-MM-dd");
+        }
     }
    
 }