Support multiple file extensions with

Some bower packages ship javascript files like `jquery.min.js`, e.g. d3. This fails with today's implementation.

This PR supports multiple file extensions
* .js.gz
* .min.js
* .asdf.asfd.js.adsf

The approach has still some limitations. If one builds a bower package where a svg-font is placed in the root directory, this does not work. The svg-font-file is placed  in `images`-directory. To fix this we need to check the content, but this might have some performance drawbacks.