Allowing to set options via data attributes

I did a change to the plugin to be able to pass plugin options via data attributes, this is really helpful when we need to configure it from the backend. To set an option, just use dashes to separate words instead of camelCase notation.

Example:
```html
<div id="owl-example" class="owl-carousel" data-slide-speed="200" data-stop-on-hover="true">
  <div> Your Content </div>
  <div> Your Content </div>
  <div> Your Content </div>
  <div> Your Content </div>
  <div> Your Content </div>
  <div> Your Content </div>
  <div> Your Content </div>
</div>
```