Add params cssPattern and jsPattern to modify the initial pattern

Hi,
This is really usefull for a Symfony2 project. We can add the 'asset' filter on the pattern.

Exemple : 
var wiredep = require('wiredep')({
  [...],
  cssPattern: '\<link rel="stylesheet" href="{{ asset(\\'\<filePath\>\\') }}" /\>',
  jsPattern: '\<script src="{{ asset(\\'\<filePath\>\\') }}"\>\</script\>'
});