Init browser if document has already loaded

I had problems embedding Dalliance as I instantiated the browser after the load event has been fired. This commit adds a check if `document.readyState` is already `complete` in which case `realInit()` is called right away. According to [MDN](https://developer.mozilla.org/en-US/docs/Web/API/document.readyState) `document.readyState === 'complete'` is equal to the load event.