Order of scripts is important when they are dependent on libraries or other scripts.
Any jQuery related code needs to be included after jQuery.js... that means plugins and any code you write that uses jQuery. Similarly any code you write that uses a plugin must have the plugin loaded before your code
Simply switch the order so jQuery.js loads before dataTables.js
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script type="text/javascript" charset="utf8" src="/js/jquery.dataTables.js"></script>
Also make sure you only ever include jQuery once in a page...not once per plugin as some occasionally do