Enabling more strong emphasis inside the quote

If we put more than one Markdown `**strong emphasis**` into the quote, makes it fail to "enrich" content.

Example:

```
> **Info** Text inside a box that accepts *italic* and **bold** emphasis.
```
Without the changes in this pull request, it renders:

![not_enriched](https://cloud.githubusercontent.com/assets/258331/4481986/20444ae6-49a4-11e4-8d3a-ecd908deda1a.png)

With improvements on selection of the config text and on css, it renders:

![enriched](https://cloud.githubusercontent.com/assets/258331/4482012/54738a20-49a4-11e4-9d8d-3bf6f6876fd0.png)

I've also tested with several strong and regular emphasis and it worked.