Minified CSS contains wrong reference to fontawesome

The minified version of the generated main.min.css file contains a wrong URL to the fontawesome font. As a result, projects that use the minified CSS do not include fontawesome.

Steps to reproduce:
1. change the stylesheet in demo/index.html.html from
<link rel="stylesheet" href="../target/dist/css/main.css">
to
<link rel="stylesheet" href="../target/dist/css/main.min.css">
2. open Hippo Theme ('grunt server')

Expected: no warning in the JavaScript console
Actual: the following 404s are logged in the JavaScript console:

GET http://localhost:9000/target/dist/css/target/dist/fonts/fontawesome-webfont.woff?v=4.2.0
GET http://localhost:9000/target/dist/css/target/dist/fonts/fontawesome-webfont.ttf?v=4.2.0