Updating EXAMPLES.md to include beneathdata.com custom example

I'd love to add my site to the pelican-boostrap3 examples list if that's ok. This has been been an outstanding framework to work with! 

This might also be a good place to ask if the banner implemented on my site would be a welcome addition to pelican-bootstrap3 as an optional setting. The idea came from Jekyll's [Cactus](http://wolfr.github.io/cactus-jekyll-theme/), which is one of the few clean, good-looking banners I've seen on a Bootstrap site. I'd need to do a bit more work to clean up my code before a PR, so before I go down that path let me know if you'd welcome the feature.