Custom filenames aren't recognized

If you upload a Fontello bundle that has a custom file name set (using the input on the left of 'Download webfont' on fontello.com) the module doesn't recognize the css files, and doesn't include them.

This could be solved in the following ways:

• Explicitly noting the default filename as a requirement, both in the interface and in the documentation.
• Possibly showing an error after upload if the fontello.css file couldn't be found.

Even nicer, of course, would be support for custom file names, but I'm not familiar enough with Fontello to know how complicated that would be.