In the `RequestUtils.getTypeByExtension()` method, the "webm" extension is there twice (line [110](https://github.com/CreateJS/PreloadJS/blob/master/src/preloadjs/utils/RequestUtils.js#L110) and line [114](https://github.com/CreateJS/PreloadJS/blob/master/src/preloadjs/utils/RequestUtils.js#L114)). Is this intended? I don't see how it could be detected as anything but `createjs.Types.SOUND` and I'm not sure this is necessarily the best default value for the WebM format. I understand that we should specify the type explicitely but I stumbled upon that, while debugging a related issue, and figured I should report it.