It seems a confusion with usage of `cssFontsUrl` and `cssFontsPath` options.
Hi!
I found out that if I try to assign some value to `cssFontsUrl` - it doesn't work as expected.
In `index.js` of webfonts-loader there is a `generatorOptions` object with `cssFontsUrl`:
```
var generatorOptions = {
    ...
    cssFontsUrl: fontConfig.cssFontsUrl || '',
    ...
  };
```
It finds appropriate propety in `fontConfig` (for example, it exists) and gets it.
But in condition of reassigning path on 131 line it checks `fontConfig.cssFontsPath`, which doesn't exists:
```
if (fontConfig.cssFontsPath) {
    generatorOptions.cssFontsPath = path.resolve(this.context, fontConfig.cssFontsPath);
}
```
so `generatorOptions.cssFontsPath` get `undefined` value and in futher in webfonts-generator code goes `undefined` too.

Actually, i was trying to get `"./IconFont.dd ... "` path in css @font-face's `src`  instead of `"/IconFont.dd ... "`, because in production mode css doesn't see generated fonts =)