Issue 6

This change addresses https://github.com/Wikia/vignette-js/issues/6
@mklucsarits Bower lets you install 'old' versions so if they are not ready to upgrade they still can install 1.0.2 while we could publish version 2.0.0 and change the API to the one that make sense. I don't see why we should stagnate just because someone is using the lib. We might add some more parameters to the function later on, and this will become a unmanageable.

So I also would vote for:
```js
getThumbURL(url: string, options: OptionsInterface): string;
```