pass an options hash/object to init

Hi, thanks for making this!

I was looking to use this on a project and found the init method a bit hard to grasp with all the arguments so I made it into an options hash. This allows you to initialize a progress bar like so:

```javascript
progBar = circularProgressBar.init({
    radius: 100, 
    width: 20,
    container: $('#progress-bar'), 
    activeColor: 'green',
    innerColor: 'tomato',
    initialPercentage: 33
});
```