Odoo v8.0 way is to add corresponding record in the XML file:
Add XML file to the manifest (i.e. __openerp__.py file.):
...
'data' : [ 'your_file.xml' ],
...
Then add following record in 'your_file.xml':
<openerp>
<data>
<template id="assets_backend" name="your_module_name assets" inherit_id="web.assets_backend">
<xpath expr="." position="inside">
<link rel='stylesheet' href="/your_module_name/static/src/css/your_file.css"/>
<script type="text/javascript" src="/your_module_name/static/src/js/your_file.js"></script>
</xpath>
</template>
....
....
</data>
</openerp>