Control HTML of linkified URLs in text

My attempt at solving #9

Added options to control the HTML used to linkify typed urls.

Defaults to `<a href="http://yahoo.com" data-cke-saved-href="http://yahoo.com">http://yahoo.com</a>' -- can be changed, e.g., to `<span class="url">http://yahoo.com</span>` with the following in CKEDITOR's config file:

```
config.autocorrect_recognizeUrlsTag = 'span';
config.autocorrect_recognizeUrlsTagAttribs = {'class': 'url'};
```

Margic value of `url` for `autocorrect_recognizeUrlsTagAttribs` results in default linkified attributes...