Change Relative Links to New Location

[BrokenEagle]

With the switch of directories that happened with Danbooru issue #2798, the HTML no longer pulls from the correct locations for the additional resources such as the JS and CSS files.

<script src='/reports/assets/jquery-3.1.1.slim.min.js'></script>
<script src='/reports/assets/jquery.tablesorter.min.js'></script>
<link href='/reports/assets/pure.css' rel='stylesheet'>

The links for all of the above should change "reports" to "user-reports".