add prompt to 404 & 500 pages to check logs

When new programmers push their code to a production server and receive an error they often don't know to check the logs, this simple reminder will help. Most professional applications have custom error pages so this change shouldn't affect them. The wording of the message should not confuse non-developer visitors.

railties/lib/rails/generators/rails/app/templates/public/404.html

@@ -22,5 +22,6 @@
     <h1>The page you were looking for doesn't exist.</h1>
     <p>You may have mistyped the address or the page may have moved.</p>
   </div>
+  <p>If you are the application owner check the logs for more information.</p>
 </body>
 </html>

railties/lib/rails/generators/rails/app/templates/public/500.html

@@ -21,5 +21,6 @@
   <div class="dialog">
     <h1>We're sorry, but something went wrong.</h1>
   </div>
+  <p>If you are the application owner check the logs for more information.</p>
 </body>
 </html>