Support for Pastebin embeds

I like to use Pastebin for adding code snippets to my blog. At the moment, there is no margin under the paste, which makes it look kinda weird:

![selection_037](https://cloud.githubusercontent.com/assets/1234006/5232821/7e86e86c-775c-11e4-9901-14158f513773.png)

With the 4 added lines, we get this:

![selection_038](https://cloud.githubusercontent.com/assets/1234006/5232824/c6eb472e-775c-11e4-9f18-763091c0aa67.png)

Any chance we get something *like* this into Casper ? Would be awesome !