Add share buttons using Duo Search

[hoffmabc]

This adds listing sharing buttons for Facebook, Twitter and Reddit via Duo Search.

Pinging @JustinDrake as well for feedback.

Looks like this:

Also the Duo Search text is a link to their web site.

[JustinDrake]

Ok, this is very cool. Love it. I think this can really bolster sharing on social media.